GENETIC  STUDIES  ON  DKOSOPIllLA  VIRILIS 

WITH  CONSIDERATIOiXS  ON 

THE  GENETICS  OF  OTHER  SPECIES  OF 

DROSOPHILA 


BY 


Charles  W.  Metz,  Mildred  S.  Moses, 
AND  Eleanor  D.  Mason 


QH43 

M53 


Published  by  the  Carnegie  Institution  of  Washington 
Washington,  July,  1923 


i 


IM53 

N^urtfj  QIarolttta  01atp 


THIS  BOOK  IS  DUE  ON  THE  DATE 
INDICATED  BELOW  AND  IS  SUB- 
JECT TO  AN  OVERDUE  FINE  AS 
POSTED  AT  THE  CIRCULATION 
DESK. 


1982 
,DEe^2 1 1983 


innhA  /in  or> 


GENETIC  STUDIES  ON  DROSOPIIILA  VIRILIS 

WITH  CONSIDERATIOxNS  ON 

THE  GENETICS  OF  OTHER  SPECIES  OF 

DROSOPHILA 


BY 


Chakles  W.  Metz,  Mildred  S.  Moses, 
AND  Eleanor  D.  Mason 


Published  by  the  Carnegie  Institution  of  Washington 
Washington,  July    1923 


CARNEGIE  INSTITUTION  OF  WASHINGTON 

Publication  No.  328 


Copies  of  tliis  iKWk 

first  issued 
JUL  27  192.- 


JUDD  &  DETWEILEB,  I>'C.,   WASHINGTON.   D.    C. 


CONTENTS. 


Page 

I.  Introductory 5 

General  Introduction 5 

Chromosome  relationships 8 

Chromosomes    of    Drosophila 

virilis 9 

Previous     work     on     Drosophila 

virilis 10 

Present  aim  of  the  work 10 

Description  of  Drosophila  virilis  10 

Source  of  material 11 

Methods  employed 12 

Acknowledgments 13 

II.  Linkage   Group   I.     Sex-linked 

Characters 14 

Description,  origin,  and  com- 
parison of  sex-linked  charac- 
ters    14 

Sepia 14 

Yellow 15 

Fraj'ed 15 

Crossveinless 15 

Vermilion 15 

Vesiculated 15 

Oblique 16 

Singed 17 

Hairy 17 

Magenta 17 

Forked 17 

Triangle 18 

Short 18 

Cut 18 

Rugose 19 

Glazed 19 

Wax 19 

Droop 20 

Linkage   in    Group    I,   and   con, 
struction  of   X-chromosome 

map 21 

Sepia 22 

Yellow 22 

Frayed 22 

Crossveinless 22 

Vermilion 22 

Vesiculated 23 

Singed 23 

Oblique 23 

Hairy 24 

Magenta  and  forked 24 

Triangle  and  short 24 

Cut 25 

Rugose,  glazed  and  wax 26 

Droop 26 

III.  Linkage  Group  II 32 

De.scription,    origin,     and     com- 
parison   of     characters     in 

Group  II 32 

Confluent 32 

Concave 32 

Double 32 

Broken 33 


Page 

III.  Linkage  Group  II— Continued. 

Linkage  data 34 

Detection      of       linkage       in 

Group  II 34 

Confluent  and  concave 34 

Double    with    concave    and 

confluent 34 

Confluent  and  broken 34 

Cross-over    values    in    Group 

,11 .34 

Confluent  and  concave 34 

Confluent  and  double 34 

Confluent  and  broken 35 

Construction  of  second-chromo- 
some map 35 

IV.  Linkage  Group  III 35 

Description,  origin,  and  compar- 
ison of  characters  in  Group 

III 37 

Scaly 37 

Spread 37 

Hunch 3S 

Telescoped 38 

Garnet 39 

Linkage  data 39 

Detection  of  linkage  in  Group 

III 39 

Scaly  and  telescoped 39 

Steel  and  telscoped 39 

Hunch  and  telescoped 39 

Scaly,  hunch,  and  telescoped  39 

Scaly  and  garnet 40 

Hunch,       telescoped,       and 

spread 40 

Cross-over    values    in  Group 

HI 40 

Scaly  and  htmch 40 

Scaly  and  telescoped 40 

Scaly  and  spread 40 

Scaly,  hunch,  and  telescoped  40 
Scaly,     hunch,     telescoped, 

and  garnet 41 

Spread  and  garnet 41 

Construction    of     third-chromo- 
some map 41 

V.  Linkage  Group  IV 43 

Description  and  origin  of  char- 
acters in  Group  IV 43 

Acute 43 

Pinched      44 

Hump 44 

Linkage  data 44 

Detection  of  linkage  in  Group 

IV 44 

Acute  and  pinched 44 

Acute  and  iiump 44 

Pinched  and  hump 45 

Complete     linkagr     of    acute, 

pinched,  and  hump 45 


1  1 7'1  :>7 


Contents. 


Page 

VI.  Linkage  Group  V 46 

Description,    origin,    and     com- 
parison    of     characters     in 

Group  V 46 

Fused 46 

Interrupted 46 

Branched 47 

Approximated 47 

Ruffled 47 

Linkage  data 48 

Detection  of  hnkage  in  Group 

V 48 

Branched  and  fused 48 

Branched  and  approximated  48 

Fused  and  interrupted 48 

Interrupted     and     approxi- 
mated   48 

Branched  and  ruffled 48 

Cross-over  values 48 

Fused  and  interrupted 48 

Fused  and  branched 49 

Fused  and  approximated ...  49 
Interrupted  and  branched  .  49 
Interrupted     and     approxi- 
mated    49 

Branched  and  ruffled 50 

Discussion 50 

V'll.  Linkage  Gnoup  VI 51 

Bent 51 

Linkage  tests  with  bent 52 

Net 52 

VIII.  Additional  Characters 54 

Extra 54 

Spine 54 

Capsule 54 

Minus 55 

IX.  Comparison  of  mutant  characters 
in  D.  virilis  with  those  in  other 

species  of  Drosophila 56 


Page 

IX.  Comparison  of  mutant  characters 
— Continued. 

Comparison  of  sex-linked  char- 
acters   57 

Forked  and  singed  series 57 

In  D.  melanogaster 59 

In  D.  mrilis 60 

In  D.  willistoni 60 

In  D.  obscura 60 

In  D.  simulans 60 

In  D.  funebris 60 

Relationships 61 

Comparison     with     sex-linked 

characters  in  D.  melanogaster  63 
Comparison     with     sex-linked 

characters  in  D.  simulans. .  .  64 
Comparison     with     sex-linked 

characters  in  D.  willistoni.  .  64 
Comparison     with     sex-linked 

characters  in  D.  obscura.  ...  65 
Comparison     with     sex-linked 
characters  in  D.  funebris.  ...  66 
Comparison  of  autosomal   char- 
acters    66 

X.  The  case  of  vermilion,  and  the  possi- 
bility of  a  rearrangement  of  genes  69 
XI.  Comparison      of      X-chromosome 

maps 71 

XII.  Coincidence 75 

XIII.  Chromosomes  and  linkage  groups 

compared 77 

XIV.  Tabulation  of  linkage  experiments  79 

Group  1 79 

Group  II 90 

Group  III 90 

Group  IV 90 

Group  V 91 

XV.  Literature  cited 93 


GENETIC  STUDIES  ON  DROSOPIIILA  VIRILIS. 


I.  INTRODUCTORY. 

GENERAL  INTRODUCTION. 

In  most  groups  of  animals  and  plants,  including  those  susceptible 
to  genetic  study  through  intensive  breeding,  the  chromosome  groups 
of  related  species  show  a  high  degree  of  uniformity.  The  different 
members  of  a  genus,  for  instance,  usually  differ  relatively  little  in 
this  regard.  In  some  cases  the  uniformity  may  extend  even  to  sub- 
families or  families,  as,  for  example,  in  the  Acridida?  among  the 
Orthoptera,  where  all  of  approximately  40  genera  studied  agree 
in  having  essentially  the  same  chromosome  group  (cf.  McClung, 
1914;  Harvey,  1916).  It  would  seem  probable,  a  priori,  that 
where  many  related  species  exhibit  such  a  constancy  in  chromosome 
groups,  the  apparent  homology  of  chromosomes  is  real,  i.  e.,  similar 
chromosomes  in  different  species  are  essentially  alike  in  genetic 
make-up.  On  the  other  hand,  there  are  various  exceptions  to  the 
general  rule  of  constancy,  and  a  number  of  cases  are  known  in  which 
closely  related  species  have  very  dissimilar  chromosome  groups. 
Hence  it  may  be  argued  that  even  where  a  constancy  exists  it  may 
be  superficial  and  not  dependent  upon,  or  significant  of,  a  likeness 
in  genetic  constitution  of  similar  chromosomes.  In  fact,  very  little 
is  known  as  to  how  far  morphological  criteria  are  trustworthy  as 
indications  of  homology  between  chromosomes.  In  one  case  recently 
investigated  by  Lancefield  and  Metz  (1921,  1922),  the  results 
indicate  that  genetic  homology  does  not  correspond  to  morpho- 
logical similarity  as  regards  two  pairs  of  chromosomes  in  Drosophila 
willistoni  compared  with  two  similar  pairs  in  D.  vielanog aster. 

These  and  other  considerations  serve  to  emphasize  the  necessity 
of  learning  something  of  the  genetic  constitution  of  chromosomes 
before  they  can  safely  be  compared  from  the  evolutionary  standpoint. 
It  is  believed  that  the  only  method  of  obtaining  rehable  information 
on  chromosome  evolution  is  by  means  of  genetic  analysis  combined 
with  cytological  observation. 

Ideal  material  for  such  a  study  would  be  provided  by  a  group  of 
species  satisfying  the  following  four  requirements:  In  the  first 
place,  it  should  exhibit  among  its  members  a  series  of  different 
chromosome  groups;  secondly,  the  species  should  be  susceptible  to 
intensive  breeding  under  controlled  conditions;  in  the  third  place, 
one  or  more  of  the  species  should  be  favorable  for  genetic  analysis 
through  the  study  of  mutant  races;  and  lastly,  the  species  should 
hybridize  with  one  another  and  give  fertile  hybrids. 

5 


D.  H.  HILL  LIBRARY 
North  Carolina  State  College 


6  Introductory. 

Many  cases  of  species  hybrids  are  known,  and  some  have  been 
studied  extensively.  Those  involving  domestic  or  semidomestic 
animals,  e.  g.,  the  mule,  ducks,  pheasants,  etc.,  are  too  well  known 
to  need  more  than  a  mention,  as  are  also  those  of  numerous  cultivated 
plants.  Likewise,  various  kinds  of  fish  hybrids  have  long  been 
familiar.  The  work  of  Federley  (1914,  1915)  and  Harrison  and 
Doncaster  (1914)  has  revealed  the  fact  that  hybridization  is  readily 
obtained  in  some  families  of  Lepidoptera.  That  of  de  Vries,  Davis, 
Bartlett,  and  others  on  Oenothera  and  of  East  and  others  on  Nicotiana 
has  demonstrated  the  same  thing  for  these  groups.  The  list  might 
be  continued  at  length,  but  the  examples  given  include  many  of  the 
most  thoroughly  studied  cases.  None  of  the  groups  known  to  be 
favorable  for  hybridization,  however,  fulfils  the  other  requirements 
necessary  for  a  detailed  study  of  chromosome  relationships,  such  as 
we  are  considering  here. 

The  genus  Drosophila  has  long  been  known  to  include  species  that 
are  excellent  for  breeding  purposes,  and  the  pioneer  work  of  Morgan 
and  others  on  D.  melanogaster  indicated  that  this  species,  at  least, 
mutates  frequently  enough  to  provide  ample  material  for  genetic 
analysis.  Consequently,  when  it  was  found  (Metz,  1914)  that  other 
species  of  Drosophila  differed  from  melanogaster  and  from  one  another 
in  respect  to  their  chromosomes,  it  was  recognized  that  the  material 
offered  unusual  possibilities  for  a  study  of  chromosome  relationships 
and  chromosome  evolution.  The  only  uncertainty  was  with  regard 
to  the  possibility  of  hybridization.  If  favorable  in  that  respect,  all 
of  the  above  requirements  would  be  fulfilled.  With  this  in  mind, 
an  extensive  series  of  tests  was  carried  out  cooperatively  by  Dr.  A.  H. 
Sturtevant  and  one  of  us  (Metz)  during  1914  and  1915,  involving 
most  of  the  species  obtainable  in  the  United  States  and  Cuba,  save 
those  that  were  not  at  all  amenable  to  laboratory  treatment.  The 
results  of  these  tests  were  all  negative,  however.  This  presented  a 
serious  difficulty,  since  it  indicated  that  if  such  a  comparative  study 
were  undertaken  with  this  material  it  would  be  necessary  to  make 
separate  genetic  studies  of  selected  species  and  then  compare  the 
results. 

However,  an  excellent  foundation  for  such  an  investigation  was 
provided  by  the  well-known  observations  on  D.  melanogaster;  and 
since  a  study  of  this  kind  promised  to  be  of  interest  in  several  addi- 
tional respects,  it  was  undertaken. 

It  should  be  noted  at  this  point  that  Dr.  Sturtevant  has  recently 
succeeded  in  hybridizing  D.  melanogaster  and  D.  simulans  (Sturte- 
vant, 1920)  with  very  interesting  results.  For  the  purposes  outlined 
above,  however,  the  possibilities  here  are  limited.  The  two  species 
are  almost  identical  and  appear  to  have  identical  chromosome 
groups,  and  in  addition  the  Fi  hybrids  are  sterile,  so  that  only  mutant 


General  Introduction. 


"      " .    II .    II 

^^^^fc  ^^^^^  ^^^^^  ^       ^  ^^^  •  ^^^^ 

M.       M         II        ^ 


!?>  ^^.-^         II         M 


r^       f\\ 


Al 

?    J   o 


9   K  d"  _  . 

^  ?    L    c? 

Fig.  1. — Types  of  Drosophila  chromosome  groups.     (From  Metz,   19166).     All  but  type  H 
are  found  in  the  genus  Drosophila.    H  is  from  Cladochaeta  nebulosa  Coq. 

n      ir       II       II 

^    D.  melanogaster     d"  D.simulans  O.virilis 


^^^ 


Jj^ 


C>      •      C^  _  ,  ^ ^  ^ 


At 


D.funebris  D  willistoni  o       D.  obscura      cC 

Fig.  2. — Chromosome  groups  of  species  of    Drosophila    which    are  being    studied    genetically. 


r 


8  Introductory. 

genes  obtained  in  both  species  can  be  used  for  comparison.    Further 
details  concerning  this  case  are  given  in  a  later  section. 

Owing  to  the  fact  that  the  material  for  the  present  work,  and  for 
other  investigations  of  a  similar  kind,  has  been  selected  largely  on 
the  basis  of  apparent  chromosome  relationships,  these  may  be  con- 
sidered briefly  here. 

CHROMOSOME  RELATIONSHIPS. 

The  known  types  of  chromosome  groups  found  in  the  genus 
Drosophila,  with  the  addition  of  one  type  from  the  related  genus 
Cladochceta,  are  represented  in  figure  1  (from  Metz,  19166).  A 
detailed  comparison  of  the  various  types  is  given  in  the  paper  just 
cited,  and  we  may  hmit  ourselves  to  features  concerning  the  species 
under  genetic  observation.  The  types  represented  by  the  latter 
are  shown  in  figure  2.^  In  this  figure  the  sex  chromosomes,  where 
identified  are  represented  in  solid  black,  and  where  not  definitely 
known,  the  ones  presumed  to  be  the  sex  chromosomes  are  cross-ruled. 
Considering  first  the  sex  chromosomes,  it  may  be  noted  that  two 
main  kinds  are  involved — the  short,  rod-like  form  found  in  D. 
melanogaster,  simulans,  and  virilis,  and  the  long  V-shaped  form 
found  in  willistoni  and  obscura.  In  funebris  the  sex  chromosomes 
have  not  been  identified,  although  the  behavior  of  the  longest  pair 
suggests  that  it  represents  the  sex  chromosomes. 

Comparing  the  autosomes,  it  is  seen  that  the  same  two  sorts  are 
represented — short  rods  and  long  V's — in  addition  to  the  small, 
dot-like  pair  common  to  all  save  possibly  D.  willistoni.  In  both  the 
autosomes  and  the  sex  chromosomes,  it  is  to  be  noted  that  the 
V-shaped  members  are  approximately  twice  the  size  of  the  rod-like 
ones  (with  the  exception  of  one  pair  in  D.  funebris)  and  that  each 
has  a  constriction  in  the  middle.  This  suggests  a  possible  relation- 
ship between  the  types  which  may  best  be  appreciated,  perhaps,  by 
imagining  all  of  the  V-shaped  chromosomes  broken  in  the  middle, 
at  the  point  of  constriction.  With  this  alteration  all  of  the  groups 
conform  essentially  to  one  type,  that  represented  by  D.  virilis. 

For  the  present  purposes,  this  series  of  chromosome  groups  repre- 
sents an  almost  ideal  condition.  There  are  clear-cut  differences 
between  the  types,  yet  the  differences  do  not  appear  to  be  purely 
at  random,  and  it  is  possible  to  compare  the  individual  tjT)es,  chro- 
mosome for  chromosome. 

The  relations  between  the  types  suggest  the  hypothesis  that  the 
latter  have  arisen  by  a  process  involving  the  breaking  up  of  large 
V-shaped  chromosomes  into  rods  or,  vice  versa,  by  the  fusion  of  rods 
to  form  V's.  If  this  hypothesis  is  correct,  genetic  analysis  should 
reveal  the  fact  through  the  resemblance  between  groups  of  linked 

*  Exclusive  of  two  or  three  species  which  have  only  been  studied  slightly. 


Chromosome  Relationships.  9 

characters,  or  portions  of  such  groups,  in  the  different  species. 
For  instance,  each  of  the  large  non-sex-Hnked  groups  of  characters 
in  D.  melanog aster  should  resemble  two  of  the  groups  in  virilis  com- 
bined, while  the  sex-linked  groups  should  correspond  in  the  two 
species.  This  is  only  one  of  the  possible  hypotheses  to  cover  the 
case,  but  it  will  serve  to  illustrate  the  mode  of  attack. 


»  2  3 

Fig.  3. — Camera  lucida  drawings  of  chromosomes  of  Drosophila  virilis.     1  and  2  from  ovarian 

cells,  3  from  a  spermatogonia!  cell. 

Such  considerations  are,  of  course,  based  on  the  assumption  that 
homologous  mutant  characters  may  be  found  in  the  species  concerned. 
The  validity  of  this  assumption  is  becoming  more  and  more  probable 
as  the  work  progresses  (see  below),  and  the  question  now  hinges 
mainly  on  whether  or  not  a  sufficient  number  of  homologous  charac- 
ters may  be  obtained  for  the  purpose. 

CHROMOSOMES  OF  DROSOPHILA  VIRILIS. 

The  chromosome  group  of  D.  virilis,  as  noted  above,  consists  of 
6  pairs,  5  of  which  are  rod-like  and  of  approximately  the  same  size, 
and  1  of  which  is  small  and  spherical.  The  small  pair  normally  lies 
in  the  center  of  the  figure  during  metaphase,  as  shown  in  the  accom- 
panying figures  (fig.  3).  In  size,  position,  and  behavior  this  pair 
agrees  with  the  similar  pair  in  most  other  species  of  Drosophila 
(Metz,  19166). 

The  five  pairs  of  rod-like  chromosomes  have  a  terminal  spindle- 
fiber  attachment  and  hence  are  usually  arranged  radially  in  metaphase 
(figs.  1  and  2,  Metz,  1916a).  As  in  other  species  of  Diptera,  homol- 
ogous chromosomes  are  normally  associated  in  pairs  in  the  somatic 
cells,  as  well  as  in  the  germ  cells.' 

In  some  figures  one  of  the  five  rod-like  pairs  appears  to  be  slightly 
longer  than  the  others,  suggesting  that  it  may  represent  the  sex 
chromosomes.  But  since  no  pair  is  conspicuously  dimorphic  in  the 
male,  this  view  has  not  been  corroborated.  It  seems  practically 
certain,  however,  from  both  cytological  and  genetic  evidence,  that 
one  of  the  rod-like  pairs,  and  not  the  small  spherical  pair,  is  the 
sex-chromosome  pair. 


1  For  a  discussion  of  this  feature  see  Metz,  1916a. 


10  Introductory. 

PREVIOUS  WORK  ON  DROSOPHILA  VIRILIS. 

In  earlier  papers  on  Drosophila  virilis  (Metz  and  Metz,  1915; 
Metz,  1916c,  1916d,  1918,  1920;  Weinstein,  1920)  it  has  been  shown 
that  the  genetic  behavior  of  this  species  agrees  in  a  general  way  with 
that  of  the  well-known  D.  melanogaster  and  that  some  of  its  mutant 
characters  bear  a  striking  resemblance  to  those  of  melanogaster. 
In  genetic  behavior,  for  instance,  the  two  species  agree,  (1)  in  that 
''crossing-over"  occurs  only  in  the  female,  (2)  in  that  the  Y  chro- 
mosome appears  to  be  functionless  as  far  as  the  ordinary  Mendelian 
characters  are  concerned,  and  (3)  in  that  the  number  of  groups  of 
linked  characters  agrees  with,  or  at  least  does  not  exceed,  the  haploid 
number  of  chromosomes.  In  regard  to  the  resemblance  between 
mutant  characters,  it  has  been  found  that  the  four  characters  con- 
fluent, yellow,  forked,  and  crossveinless  are  sufficiently  similar  in 
the  two  species  to  give  some  ground  for  believing  them  to  be  homolo- 
gous, and  that  the  likeness  between  certain  others  suggests  a  similar 
relation. 

PRESENT  AIM  OF  THE  WORK. 

With  the  completion  of  the  preliminary  tests,  concerning  the 
general  genetic  behavior  of  D.  virilis,  attention  was  directed  partic- 
ularly to  the  genetic  analysis  of  the  chromosomes  by  means  of  mutant 
characters,  and  a  detailed  comparison  of  the  results  with  those 
obtained  in  other  species  of  Drosophila.  The  latter  feature,  and  the 
work  of  the  different  investigators  involved,  is  considered  in  detail 
in  later  sections.  It  may  be  stated  at  the  outset  that  the  studies 
have  not  yet  progressed  to  the  point  of  giving  final  answers  to  the 
main  questions  toward  which  they  are  directed.  The  aim  of  the 
present  paper,  therefore,  is  primarily  to  bring  together  the  data 
and  to  indicate  the  trend  of  the  results  thus  far  obtained.  For 
this  reason  it  is  largely  descriptive.  The  descriptive  part  is  also 
emphasized,  necessarily,  because  of  the  fact  that  detailed  information 
concerning  both  the  appearance  and  the  genetic  behavior  of  mutant 
characters  is  necessary  before  those  of  different  species  can  be  com- 
pared satisfactorily. 

DESCRIPTION  OF  DROSOPHILA  VIRILIS. 

The  following  taxonomic  description  of  D.  virilis  Sturtevant  is 
taken  from  Sturtevant's  (1921c)  "The  North  American  species  of 
Drosophila,"  p.  97: 

"&,  9  .  Arista  with  about  five  branches  above  and  two  below.  AntennjE  brown, 
third  joint  dark  opaque  reddish-brown.  Front  over  one-third  width  of  head,  wider 
above;  dull  coffee-brown,  ocellar  dot  black.  Second  orbital  one-third  other  two. 
Second  oral  bristle  three-quarters  length  of  first.  Only  one  long  bristle  on  each 
palpus.  Carina  broad,  slightly  sulcate,  nose-like;  face  somewhat  shiny,  brown. 
Cheeks  yellowish  brown;  their  greatest  width  over  one-fourth  greatest  diameter  of 
eyes.     Eyes  pilose. 


Source  of  Material.  11 

"Achrosticlial  hairs  in  six  rows;  no  prescutellars.  Mcsonotum  and  scutellum  dark 
dull-brown.  Pleura;  and  abdomen  dull  brown,  somewhat  darker.  Legs  pale  brown . 
Apical  and  preapical  bristles  on  first  and  second  tibiae,  preapicals  on  third. 

"Wings  clear,  veins  brown.  Costal  index  about  2.8;  fourth-vein  index  about  1.8; 
5x  index  about  1.2;  4c  index  about  0.9. 

"Length  body  2.8  mm.;  wing  3.0  mm. 

"The  eggs  have  four  filaments.  The  females  do  not  ordinarily  begin  to  lay  until 
they  are  4  or  5  days  old.    About  3  weeks  are  required  for  development. 

"The  small  eyes  and  broad  cheeks  make  this  species  obviously  distinct  from  such 
types  as  D.  robusta  that  resemble  it  superficially." 

Supplementary  to  the  above,  especial  attention  may  be  called  to 
certain  characteristics  that  are  particularly  noticeable  in  living 
specimens  or  that  need  to  be  kept  in  mind  in  considering  the  com- 
parison of  mutant  characters  with  those  of  other  species:  The  dark 
dull-brown  body-color  and  large  size  of  D.  virilis  contrast  sharply 
with  the  yellowish  gray  color  and  small  size  of  such  species  as  D. 
melanog aster,  D.  simulans,  and  D.  willistoni.  The  color  more  nearly 
resembles  that  of  D.  ohscura,  but  is  duller  and  lighter.  It  is  duller 
and  darker  than  that  of  D.  funehris  and  lacks  the  olive  tone  of  the 
latter.  The  eyes  of  D.  virilis  are  dark,  dull,  reddish  brown,  more 
opaque  than  those  of  melanog  aster,  simulans,  willistoni,  or  ohscura. 
Virilis  males  do  not  possess  the  tarsal  "sex-combs"  found  in 
melanogaster,  simulans,  and  ohscura.  In  this  respect  they  agree  with 
the  males  of  willistoni  and  funehris.  A  wild-type  or  normal  male 
of  D.  virilis  is  shown  in  figure  1  of  plate  1. 

SOURCE  OF  MATERIAL. 

The  original  stock  of  Drosophila  virilis  Sturtevant,  used  in  our  ex- 
periments, was  derived  from  a  single  pair  hatched  from  a  pineapple 
exposed  at  Columbia  University,  in  November,  1913,  by  Dr.  A.  H. 
Sturtevant,  Nearly  all  of  our  work  has  been  based  on  descendants  of 
this  one  pair,  which  have  been  kept  in  the  laboratory,  in  bottles,  for  8 
years,  or  approximately  136  generations.  In  1919  a  second  stock  col- 
lected at  Terre  Haute,  Indiana,  was  obtained  from  Dr.  Roscoe  Hyde. 
One  mutant  character  (hump)  was  found  in  this  stock  soon  after  it 
was  secured  and  others  appeared  subsequently.  The  two  stocks  have 
been  more  or  less  intercrossed  in  the  course  of  the  experiments. 
They  appear  to  be  identical  in  all  respects  and  we  have  made  no 
effort  to  keep  them  separated. 

Since  no  other  records  of  this  species  are  known  save  one  from 
Los  Angeles,  California,  and  one  from  a  doubtful  specimen  taken  at 
Chattanooga,  Tennessee  (Sturtevant,  1.  c,  p.  97),  it  is  practically 
certain  that  our  stocks  have  never  been  contaminated  from  sources 
outside  the  laboratory. 

It  may  be  noted  in  this  connection  that  no  decrease  in  fertility 
has  been  observed  in  the  stocks  during  their  8  years'  confinement 
in  the  laboratory. 


12  Introductory. 

METHODS  EMPLOYED. 

Detailed  methods  of  treatment  of  the  data  are  given  under  the 
respective  headings  below,  but  the  following  general  features  may 
be  noted  at  this  point. 

For  the  sake  of  convenience,  a  description  of  each  mutant  type 
is  given  in  the  present  paper,  whether  it  has  been  published  previously 
or  not.  Some  of  these  include  features  that  have  previously  been 
overlooked  or  omitted.  In  connection  with  the  descriptions  brief 
notes  are  added  (under  "Comparison"),  indicating  resemblances 
to  characters  in  the  other  species,  if  such  exist.  The  absence  of 
such  comparison  indicates  that  no  similar  characters  are  known  to  us. 
These  comparisons  are  given  very  briefly,  for  a  full  consideration 
of  such  relationships  is  included  in  later  sections. 

The  terminology  used  is  that  commonly  employed  at  the  present 
time  in  animal  genetics.  Symbols  have  been  avoided  as  far  as  is 
practicable  in  the  tables  and  text,  although  they  have  necessarily 
been  used  extensively.  Recessive  mutant  characters,  or  genes,  are 
designated  by  small  letters  and  dominants  by  capitals.  Super- 
scripts are  employed  only  in  the  case  of  multiple  allelomorphs. 

In  order  to  simplify  treatment  of  the  experimental  data,  the 
name  of  a  mutant  type  is  frequently  used  to  designate  either  the 
character  itself  or  the  gene  responsible  for  the  character  or  the  locus 
of  the  gene,  without  distinction.  Although  this  usage  is  possibly 
open  to  some  criticism,  its  great  convenience  justifies  its  adoption, 
we  believe,  at  least  when  care  is  taken  to  qualify  the  expression  where 
clarity  demands. 

Since  the  purpose  of  this  study  is  comparative,  the  linkage  experi- 
ments have  been  carried  only  far  enough  to  indicate  the  relative 
order  of  the  genes  and  their  approximate  "locations"  on  the  chro- 
mosome map.  No  corrections  have  been  made  for  differential 
viability  or  double  crossing-over  in  constructing  the  maps.  Likewise, 
map  values  have  in  nearly  all  cases  been  given  in  whole  numbers. 
It  is  believed  that  any  attempt  to  make  a  more  refined  calculation  or 
to  express  values  in  decimals  would  in  most  cases  give  a  false  impres- 
sion of  accuracy.  It  is  for  this  reason,  for  instance,  that  the  method 
suggested  by  Fisher  (1922)  has  not  been  used.  For  certain  types 
of  work  the  latter  method  promises  to  be  useful,  but,  as  indicated 
by  Fisher  himself,  when  applied  to  cases  like  the  present  it  gives 
values  only  slightly  different  from  those  obtained  by  the  more  simple 
method  of  calculation  used  here. 

Several  characters  have  been  included  which  overlap  normal  to 
such  an  extent  as  to  make  them  unsatisfactory  for  detailed  linkage 
studies,  but  which  are  valuable  for  comparative  studies.  On  the 
other  hand,  sex-linked  lethals  have  been  omitted,  since  they  are  of 
little  value  for  purposes  of  comparison. 


M  ETZ 


PLAT  E    1 


'"^BW&^t  i^f^^^y 


-^^^^^^^^ 


5 


E.  M.  Wallace  Pinx. 

SEX-LINKED     MUTANT     CHARACTERS     IN      DROSOPHILA    VIRILIS 
1.    WILD-TYPE   o-  2.     YELLOW    CROSSVEINLESS  3.     FORKED" 


IVI  T-    A 


Acknowledgments.  13 

In  a  study  of  this  kind,  in  which  new  characters  are  appearing  from 
time  to  time,  there  are  always  some  on  hand  which  have  not  been 
fully  studied  in  respect  to  linkage.  This  is  true  of  several  in  the 
present  case.  These  have  been  included  for  the  sake  of  completeness, 
although  in  some  instances  little  can  be  given  beyond  the  description 
of  the  character  and  its  mode  of  origin. 

The  method  of  detecting  linkage  among  non-sex-linked  characters, 
and  thus  of  assorting  them  into  linkage  groups,  has  been  by  means 
of  F2  counts,  and  back-crosses  of  heterozygous  males.  In  the 
earlier  experiments  each  new  character  was  tested  with  representa- 
tives of  all  known  linkage  groups,  and  most  of  the  characters  have 
been  so  tested;  but  more  recently  the  tests  have  been  discontinued 
as  soon  as  a  character  was  found  to  be  linked  to  one  of  the  test  char- 
acters. The  data  from  these  purely  test  experiments  are  not  included, 
except  in  the  cases  showing  linkage. 

In  considering  each  linkage  group,  the  data  from  the  test  experi- 
ments are  all  given  first;  then  follow  the  experiments  from  which 
crossover  values  are  taken.  This  method  of  treatment  facilitates 
examination  of  the  linkage  data. 

The  order  of  the  genes  on  the  maps  has  been  determined  in  the 
usual  manner,  mainly  by  means  of  three-point  crosses.  In  the  latter 
case  the  smallest  cross-over  class  has  been  assumed  to  represent  the 
double  cross-overs  and  the  order  has  been  arranged  accordingly. 
In  a  few  cases  the  order  has  been  determined  by  ''locating"  a  gene 
with  reference  to  two  others  independently. 

The  records  of  matings  given  in  the  text  and  tables  refer  to  the 
original  laboratory  notes.  Those  not  prefixed,  or  prefixed  by  V,  L, 
or  M  are  records  of  C.  W.  Metz,  those  prefixed  by  E  are  records  of 
E.  D.  Mason,  and  those  prefixed  by  P  are  records  of  M.  S.  Moses. 

ACKNOWLEDGMENTS. 

We  are  indebted  to  Professor  T.  H.  Morgan  and  to  Doctors  A.  H. 
Sturtevant,  C.  B.  Bridges,  and  D.  E.  Lancefield  for  the  loan  of 
specimens  and  for  information  concerning  mutant  characters  in 
other  species  of  Drosophila,  and  also  for  suggestions  as  to  their 
possible  relationships  to  characters  in  D.  virilis.  Dr.  Bridges  has 
furnished  information  on  D.  melanog aster,  Dr.  Sturtevant  on  melano- 
gaster  and  simulans,  and  Dr.  Lancefield  on  obscura.  Our  indebted- 
ness is  particularly  great  to  Dr.  Sturtevant,  whose  interest  and 
cooperation  have  added  materially  to  the  progress  of  the  work  from 
its  inception.  We  likewise  acknowledge  with  gratitude  the  assistance 
of  the  following  persons,  who  made  the  drawings  and  photographs 
for  the  accompanying  figures:  Miss  E.  M.  Wallace,  figures  5  and  12 
and  plate  1;  Miss  G.  Ruth  Lincks,  figures  4  and  6;  Miss  E.  M.  Lord, 
plates  2  to  4. 


14 


Linkage  Group  I. 


II.  LINKAGE  GROUP  I.  SEX-LINKED  CHARACTERS. 

The  sex-linked  group  consists  of  18  characters.  These  are  listed 
in  table  1  in  chronological  order.  The  first  10  have  been  described 
previously  (Nos.  1  to  4,  Metz,  1916c?;  Nos.  5  to  8,  Metz,  1918;  No.  9, 
Metz,  19206;  No.  10,  Weinstein,  1920).  In  the  accompanying 
descriptions  the  order  of  treatment  is  not  chronological,  but  conforms 
to  the  order  of  the  genes  on  the  chromosome  map.  Under  each 
heading  is  given  a  description  of  the  character,  an  account  of  its 
origin,  and  a  comparison  with  similar  characters  in  other  species  where 
such  are  known. 


Table  1 

. — Chronological  list  of  sex- 

inked  characters  in  Drosophila  virilis. 

Character. 

Symbol. 

Parts  affected. 

First  ob- 
served. 

Found  by — 

Record. 

Yellow 

Magenta 

Glazed 

y 
m 

f 

r 

V8 

fd 

ha 

r" 

c 

T 

V 

se 

dp 

si 

s 

o 

ct 

Body-color 

Eye-color 

Eyes 

Jan.    1916.. 
June  1916. . 

Do. 

Do. 

Do. 
July   1916.. 
Sept.  1916.. 
Nov.  1916 

B.  S.  Metz.. 

C.  W.  Metz. 

Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Weinstein . . . 

Mason 

Metz 

Mason 

Moses 

Do. 
Metz 

Do. 

2127. 
ac  stock, 
stock. 
C  stock. 
V611. 
V290. 

V  590. 
V745. 

V  1095. 
Weinstein.  1920. 

E  1. 

L404. 

E780. 

P220. 

P384. 

M47 

M  102. 

Forked  

Bristles 

Eyes 

Rugose 

Vesiculated 

Frayed 

Wings 

Abdomen 

Hairy 

Eyes 

Wax 

Eyes 

May  1917.. 
Nov.  1917.. 

Oct.   1919.. 

Do. 
Mar.  1920.. 
Oct.    1920.. 
Nov.  1920. . 
June  1922 . . 

Do. 

Crossveinless 

Triangle 

Vermilion 

Sepia 

Wing  veins 

Wing  veins. 

Eye-color 

Eye-color 

Wings 

Droop 

Singed  

Short 

Bristles  and  hairs 

Wing  veins 

Wings 

Oblique 

Cut 

Wings 

DESCRIPTION,  ORIGIN  AND  COMPARISON  OF 
SEX-LINKED  CHARACTERS. 

Sepia  (se).     (Plate  1,  Figure  6.) 

Description. — The  only  visible  effect  of  sepia  is  on  the  eyes,  which  are  deep  opaque 
brown,  almost  lacking  in  red.  The  character  is  readily  recognized  in  both  young  and 
old  flies,  but  is  most  striking  in  young  ones. 

Origin. — (L404)  8  sepia  males  were  obtained  from  a  mating  of  2  heterozygous 
pinched  females  with  one  mosaic  (or  deformed)  male.  (The  male  may  have  been  a 
true  mosaic  or  merely  deformed  by  injury.  Its  left  wing  was  short  and  the  scutellar 
bristles  on  the  left  side  were  forked.  Evidently  its  germ-cells  were  not  affected, 
however,  for  the  character  did  not  appear  again  in  its  descendants.) 

Comparison. — Sepia  bears  a  general  resemblance  to  various  dark  eye-colors  in 
other  species  (e.  g.,  prune,  ruby,  purple  in  Drosophila  melanogaster,  and  prune  and 
plum  in  D.  simulans),  and  also  to  magenta  and  garnet  in  D.  virilis.  The  flat  or 
opaque  nature  of  the  color,  with  a  minimum  of  red  in  its  composition,  particularly 
suggests  "prune"  in  melanogaster  and  simulans. 


Description  of  Characters.  15 

Yellow  (y).     (Plate  1,  Figure  2.) 

Description.— YqWow  changes  the  ground-color  of  the  entire  fly  from  dark  brown 
to  yellow  (compare  figs.  1  and  2,  plate  1).  The  change  is  especially  noticeable  in  the 
wings,  although  it  is  readily  observable  in  body  and  legs,  especially  in  young  flics. 
Very  old  flies  are  darkened,  so  that  the  body-color  approaches  that  of  pale  specimens 
of  non-yellow  stocks.  The  color  of  the  hairs  and  bristles  in  yellow  flics  is  not  notice- 
ably different  from  normal.  They  may  be  faintly  tinged  with  bronze,  but  if  so  the 
change  is  very  slight.  Yellow  averages  slightly  later  than  normal  flies  in  hatching, 
and  has  somewhat  lowered  viability. 

Origin. — (1281,  2127.)  Several  males  appeared  in  a  mass  culture.  (See  Metz. 
1916d,  p.  599.) 

Comparison. — Yellow  resembles  the  "yellow"  of  D.  melanogaster,  D.  simnlanB, 
D.  willistoni,  and  D.  obscura,  except  for  its  brown  instead  of  bronze  or  yellow  bristles 
and  hairs.*  In  each  of  these  species  the  character  is  sex-linked,  and  it  is  possible  that 
they  are  all  homologous. 

Frayed  (fd). 

Description. — In  frayed  flies  the  dorsal  bands  of  the  pigment  on  the  abdomen  are 
frayed  out  or  irregularly  broken  at  the  ends  as  they  extend  down  the  sides  of  the 
body.  Accompanying  this  are  various  other  modifications.  Almost  the  entire  fly  is 
affected  in  some  way  (see  figs.  3  and  6,  Metz,  1918);  the  thoracic  bristles  are  reduced 
to  little  more  than  hairs;  some  of  the  bristles  on  the  head  are  entirely  gone;  frequently 
the  aristae,  and  sometimes  the  entire  antennae,  are  abortive  or  wanting;  the  wings  are 
frequently  broken  and  disarranged  in  various  ways;  and  finally,  development  is 
retarded  several  days,  so  that  frayed  flies  hatch  several  days  later  than  normal. 
Frayed  is  recessive  to  wild-type.  The  stock  was  lost  soon  after  the  character  first 
appeared,  owing  to  the  sterility  of  the  females. 

Origin. — (V  590.)  Several  males  appeared  in  a  mass  culture  (see  Metz,  1918, 
p.  110). 

Crossveinless  (c).     (Plate  1,  Figure  2.) 

Description. — This  character  is  distinguished  by  the  absence  of  the  posterior 
cross-vein  and  sometimes  part  or  all  of  the  anterior  cross-vein. 

Origin. — (See  Weinstein,  1920.) 

Comparison. — Crossveinless  resembles  the  crossveinless  of  D.  melanogaster  and 
non-sex-linked  characters  of  the  same  general  type  in  D.  obscura  and  D.  willistoni 
(unpublished  data). 

Vermilion  (v).    (Plate  1,  Figure  5.) 

Description. — Vermilion,  like  sepia,  is  an  eye-color  character.  The  color  is  near 
Ridgeway's  scarlet,  but  slightly  darker  and  more  yellowish.  Vermilion  is  also  char- 
acterized by  the  presence  of  the  dark  fleck  in  the  eye,  which  is  absent  in  the  other 
stocks  of  virilis.  It  bears  a  close  resemblance  to  the  eye-color  of  the  wild  type  D. 
melanogaster,  with  perhaps  a  darker  tinge.  It  can  be  distinguished  from  normal  in 
flies  of  any  age. 

Origin. — (E  1.)     One  male  was  found  in  a  stock  bottle. 

Comparison. — In  appearance  vermilion  suggests  the  characters  of  the  same  name 
in  D.  melanogaster,  obscura,  and  willistoni  (unpublished  data  of  Miss  Ruth  Ferry), 
although  the  actual  color  is  considerably  darker  than  in  these  sj)ecies. 

Vesiculated  (vs).     (Plate  2,  Figure  2.) 

Description. — Vesiculated  is  characterized  by  the  presence  of  vesicles  or  blisters 
in  the  wings.     Occasionally  the  entire  wing  may  be  swollen  into  a  single  large  vesicle 

'In  the  latter  respect  it  suggests  "lemon"  in  D.  melanogaster  (Morg.in  and  Bridgei,  1916). 
In  lemon,  however,  the  males  are  infertile  and  have  low  viability,  and  the  females  are  unknown- 


16 


Linkage  Group  I. 


filled  with  liquid,  but  usually  there  is  only  a  small  blister,  or  perhaps  two  near  the 
center  of  the  wing.  Frequently  only  one  wing  is  affected,  and  ordinarily  in  from  1 
to  5  per  cent  of  the  cases  both  wings  appear  to  be  normal.  The  viability  of  vesicu- 
lated  stock  is  good,  and  aside  from  the  inconstancy  just  mentioned  the  character  is 
good  for  linkage  studies. 

Origin. — (V  290.)  Several  males  were  obtained  from  a  mass  culture  (see  Metz, 
1918,  p.  107). 

Comparison. — Vesiculated  suggests  "inflated"  in  D.  melanogaster  (Weinstein, 
1918),  "bubble"  in D.  simulans  (Sturtevant  unpublished  data),  and  "inflated"  in 
D.  funebris  (Sturtevant,  unpublished  data). 


Fig.  4. — Singed. 


Oblique  (o).     (Plate  2,  Figures  3  and  4.) 

Description. — Oblique  males  differ  from  normal  in  nearly  all  parts  of  the  body. 
In  size  they  are  smaller;  in  body-color  considerably  darker;  in  eye-color  extremely 
dark,  becoming  almost  black  with  age.  The  body  is  much  shorter  and  stouter  than 
usual,  the  wings  are  short,  broad,  and  sometimes  obliquely  blunted  instead  of  being 
rounded  (fig.  3,  plate  2),  and  usually  hang  do\vn  over  the  sides  of  the  abdomen, 
roof-like,  instead  of  being  held  horizontally.  The  fifth  vein  is  often  short  and  the 
posterior  crossvein  is  often  broken  or  wanting.  Oblique  females  are  sterile  and  conse- 
quently pure  stock  has  not  been  obtained.  The  name  of  this  character  was  taken 
from  its  appearance  in  combination  with  short.  In  this  combination  both  char- 
acters are  exaggerated;  the  wings  are  frequently  very  short  and  cut  off  obliquely  at 
the  tips  (fig.  4,  plate  2),  and  the  veins  are  shortened  more  than  in  ordinary  "short" 
flies. 

Origin. — (M  47.)  16  oblique  males  were  found  among  the  offspring  of  2  females 
heterozygous  for  vermilion  and  short. 


Description  of  Characters.  17 

Singed  (si).     (Figure  4.) 

Description. — Singed  affects  the  bristles  and  hairs,  particularly  on  the  body  and 
legs.  The  bristles  are  shortened  and  depressed  and  are  twisted  and  curled,  as  if 
singed.  The  hairs  are  likewise  depressed  and  sometimes  curled.  The  hairs  in  the 
wings  are  affected  slightly,  if  at  all.  Those  on  the  costa  lie  in  approximately  a  normal 
position,  instead  of  standing  out  at  an  angle  from  the  wing,  as  they  tend  to  do  in 
forked  flies.  The  eggs  and  the  body-color  are  normal,  or  very  near  normal.  The 
character  is  ordinarily  used  as  a  recessive,  and  is  the  same  in  males  and  in  homo- 
zygous females.  It  is  possible  to  distinguish  heterozygous  females  from  the  wild  type, 
however,  by  their  shorter,  less  tapering  bristles.  Singed  flies  have  good  viability, 
and  both  sexes  are  fertile,  making  the  character  one  of  the  most  useful  for  linkage 
studies. 

Origin. — (P.  220.)     A  single  male  was  obtained  from  glazed  stock. 

Comparison. — (See  page  60.) 

Hairy  (ha). 

Description. — Superficially  hairy  resembles  "rugose,"  but  it  lacks  the  light  color 
of  the  latter  and  has  a  sprinkling  of  heavy  black  hairs  over  the  eye-surface,  giving  it 
a  peculiar  bushy  appearance  entirely  wanting  in  rugose.  Typical  specimens  of 
hairy  are  readily  recognized,  but  the  character  varies  considerably  and  is  not  always 
readily  distinguished.  The  stock  was  discarded  after  a  few  linkage  experiments  were 
completed. 

Origin. — (V  745.)  One  male  was  found  among  the  offspring  of  a  single  pair. 
(See  Metz,  1918,  p.  60.) 

Magenta  (m).     (Plate  1,  Figure  7.) 

Description. — Magenta  is  very  similar  to  sepia,  but  is  slightly  more  reddish  in 
tone  and  is  a  "deeper"  or  more  "liquid"  color  instead  of  being  "flat,"  as  in  the  case 
of  sepia.  The  character  is  more  marked  in  the  males  than  in  the  females,  but  is 
usually  readily  recognizable  in  either  sex.  It  is  almost,  if  not  quite,  indistignuishable 
from  the  third  chromosome  dominant  "garnet."  The  viability  of  magenta  flies  is 
excellent  and  the  character  is  one  of  the  best  for  linkage  studies. 

Origin. — Magenta  was  first  observed  in  half  of  the  sons  of  an  "acute"  female. 
(Metz,  1918,  p.  599.) 

Comparison. — Magenta  suggests  "garnet"  in  D.  melanogasfer  and  "carmine"  in 
D.  simulans. 

Forked  (f).     (Plate  1,  Figure  3.) 

Description. — In  forked  flies  the  bristles  on  the  head,  thorax,  and  legs  are  shorter 
and  stouter  than  usual,  are  often  irregularly  twisted,  or  bent  at  sharp  angles,  and  a 
few  are  usually  forked.  The  hairs  are  not  greatly  affected,  but  are  somewhat  stouter 
and  less  tapering  than  usual.  The  thorax  is  darkened  and  has  a  characteristic 
glossy  appearance.  Males  and  homozygous  females  are  similar;  heterozygous  females, 
like  those  of  singed,  have  the  bristles  slightly  shortened.  The  eggs  appear  to  be 
normal. 

Forked  resembles  singed  in  its  affect  on  the  bristles  and  hairs,  but  is  much  less 
extreme  than  the  latter.  The  bristles  and  hairs  are  not  flattened  do\vn  or  tightly 
twisted  as  in  singed.  On  the  legs  they  are  only  slightly  affected  in  forked,  while 
they  are  markedly  affected  in  singed  flies.  The  marginal  hairs  on  the  costal  vein  of 
the  wing  stand  out  at  a  greater  angle  than  usual,  especially  toward  the  back  of  the 
wing. 

In  singed  the  hairs  on  the  abdomen  are  twisted  and  depressed,  while  in  forked 
they  are  almost  normal.     In  the  double  recessive  forked-singed  males  the  hairs  and 


18  Linkage  Group  I. 

bristles  resemble  singed,  but  the  presence  of  forked  is  revealed  by  the  dark,  glossy 
color  of  the  thorax.     Both  sexes  are  fertile,  but  have  poor  viability. 

Origin. — A  single  male  from  a  mating  in  which  only  one  female  parent  was  used. 
(See  Metz,  1916,  p.  600.) 

Comparison. — (See  p.  60.) 

Triangle  (T).     (Plate  2,  Figures  5  and  6.) 

Description. — Triangle  flies  usually  have  an  extra  cross-vein  between  the  costal 
and  second  veins  near  their  junction,  and  have  the  anterior  cross-vein  thickened  at 
its  junction  with  the  third  vein  (fig.  6,  plate  2).  The  latter  characteristic  can  usually 
be  detected  in  the  few  flies  that  fail  to  show  the  former.  Sometimes  the  character 
resembles  the  non-sex-linked  dominant  confluent.  Triangle  is  a  dominant  character, 
but  is  not  lethal  when  homozygous. 

Origin. — The  origin  of  triangle  is  not  definitely  known,  since  it  was  for  a  time 
confused  with  branched,  a  non-sex-linked  character.  The  separation  of  triangle  from 
branched  was  accomplished  by  Dr.  Alexander  Weinstein. 

Short  (s).     (Plate  2,  Figure  7.) 

Description. — Short  is  more  extreme  in  the  males  than  in  the  females.  In  the 
former  the  fifth  vein  is  greatly  shortened.  Usually  it  does  not  extend  much  beyond 
the  posterior  cross-vein,  and  frequently  does  not  reach  this  vein.  Approximately 
half  of  the  flies  have  the  fourth  vein  slightly  shortened  also.  In  extreme  cases  the 
cross-vein  curves  back  to  meet  the  fifth  vein,  or  is  curved  back  toward  it,  instead  of 
being  straight.  In  the  females  the  fifth  vein  is  usually  slightly  shortened,  but  the 
fourth  is  seldom  affected,  and  often  the  wings  appear  to  be  normal. 

Origin. — (P.  384.)    One  male  was  obtained  from  a  pair  mating. 

Comparison. — Short  resembles  the  character  of  the  same  name  in  D.  vnllistoni 
(Lancefield  and  Metz,  1922)  and  in  D.  obscura  (D.  E.  Lancefield,  1922). 

Cut  (ct).     (Plate  2,  Figures  8  to  10.) 

Description. — It  should  be  noted  in  connection  with  the  following  description  that 
the  gene  for  cut,  if  not  allelomorphic  to  that  for  short,  may  be  accompanied  by  short 
in  the  same  chromosome,  and  hence  the  effects  described  may  be  due  to  the  com- 
bination and  not  to  cut  alone.  Cut  flies,  of  both  sexes,  have  short,  narrow  wings, 
held  at  an  angle  from  the  body,  and  cut  in  at  the  apex,  between  the  longitudinal 
veins  (fig.  8,  plate  2).  The  cuts  vary  in  depth  from  slight  indentations  to  deep  in- 
cisions. The  venation  is  irregular;  the  costal  vein  ends  between  the  second  and 
third  veins;  the  tips  of  the  fifth,  and  sometimes  of  the  other  veins,  are  swollen,  delta- 
like; the  second  vein  occasionally  fails  to  reach  the  margin,  and  may  fork  at  the 
tip  or  send  off  a  branch  toward  the  third  vein;  the  posterior  cross- vein  is  usually 
gone  or  broken;  the  anterior  cross- vein  is  thickened,  and  lateral  branches  or  swellings 
frequently  project  from  the  longitudinal  veins.  The  more  common  positions  for  the 
latter  are  down  from  the  second  vein  and  from  the  fourth  vein  near  the  apex.  Fre- 
quently the  wings  are  very  small  and  are  swollen  or  blistered.  The  anterior  scutellar 
bristles  are  usually  gone,  or  small  and  slender,  and  the  posterior  scutellars  are  often 
erect,  or  in  abnormal  positions,  while  the  scutellum  itself  is  shorter  than  usual. 

Cut  flies  do  not  breed  readily,  but  both  sexes  are  fertile  to  some  extent  and  it  is 
possible  to  keep  pure  stock. 

In  some  (and  possibly  all)  females  heterozygous  for  cut,  the  tip  of  the  fifth  vein 
is  slightly  thickened  or  delta-like  (fig.  10,  plate  2).  This  feature  was  overlooked  at 
first,  hence  we  are  not  certain  that  it  is  constant. 

In  females  heterozygous  for  cut,  and  carrying  short  in  the  opposite  X  chromo- 
some (possibly  homozygous  for  short),  the  wings  are  smaller  than  usual,  are  held  at 
an  angle  from  the  body,  and  usually  droop  down  over  the  sides;  the  tips  of  the  fifth 


■METZ 


PLATE  2 


8 


Sex-iinkki)  Mutant  Ciiakacters  in  Dkosophii.a  viuii  i-. 

1,   Wi!(l-tyi)c:     2,  Ncsiciilatod;     3.  ()l)!i(iuc;  J,  Ol'licpio  sliort ;      ">,  Tri;in;:li>;     ti.   1  riauniL-; 

7,  Sliort;     S,  Cut;    9,  Heterozygous  short  cut  9  ;     10,  Iletcrozyudus  cut  9. 


Description  of  Characters.  19 

veins,  and  sometimes  of  the  third,  are  delta-like  (fig.  9,  plate  2) ;  the  posterior  cross- 
vein  is  sometimes  broken,  and  occasionally  the  entire  wing  is  soft  in  texture. 

The  origin  and  behavior  of  cut  are  such  that  we  are  unable  to  tell,  as  yet,  whether 
the  character  is  an  allelomorph  of  short  or  is  due  to  a  dominant  modifier  closely 
linked  to  short.  The  character  itself  seems  to  be  of  the  opposite  nature  from  that  of 
short,  increasing  instead  of  diminishing  the  size  of  the  veins,  which  argues  somewhat 
against  its  being  an  allelomorph.  On  the  other  hand,  it  should  be  noted  that  in 
females  heterozygous  for  cut  the  same  vein  (fifth)  is  affected  as  is  affected  by  short. 
The  absence  of  cross-overs  between  the  two  genes  (thus  far)  indicates  that  if  not 
allelomorphic  they  must  be  very  closely  linked. 

Origin. — (M  102.)  From  a  mating  (M  40)  of  a  female  heterozygous  for  short  and 
vermilion,  by  2  short  garnet  brothers,  approximately  200  offspring  of  the  expected 
classes  were  obtained,  and  in  addition  one  female  with  the  wings  slightly  spread  and 
the  end  of  each  fifth  vein  thickened.  This  female  proved  to  be  heterozygous  for  cut. 
Her  daughters  were  all  normal,  but  her  sons  were  of  two  classes,  approximately  half 
(19)  short  and  half  (16)  cut.  The  data  in  this  case  show  that  the  mother  of  this 
exceptional  female  was  not  heterozygous  for  cut,  else  cut  sons  and  additional  hete- 
rozygous daughters  should  have  appeared.  The  mutation  evidently  occurred  in  one 
of  the  parents  or  in  the  egg  that  gave  rise  to  this  female. 

Comparison. — Cut  shows  a  slight  resemblance  to  "bifid"  in  D.  melanogaster  (Mor- 
gan and  Bridges,  1916,  p.  29),  but  not  enough  to  make  homology  probable. 

Rugose  (r). 

Description. — This  character  derives  its  name  from  the  roughening  of  the  eye 
due  to  disarrangement  of  the  ommatidia  (fig.  4,  Metz,  1918).  The  color  of  the  eye 
is  also  affected,  being  considerably  lighter  than  normal  and  having  a  more  yellowish 
tinge.  The  eye  is  full-sized,  however,  and  the  ommatidia  are  not  coalescent,  as 
they  tend  to  be  in  the  two  following  characters  glazed  and  wax.  Rugose  is  sex- 
limited,  appearing  only  in  the  males.     Its  viability  is  excellent. 

Origin. — (V611.)  One  male  from  a  pair  mating  of  a  confluent  male  by  normal 
female  (Metz,  1918,  p.  110). 

Glazed  (r«). 

Description. — Glazed  is  a  more  extreme  eye  modification  than  its  allelomorph 
rugose.  The  ommatidia  show  greater  disarrangement,  many  are  lacking,  leaving 
smooth  spaces  on  the  eye-surface,  and  others  tend  to  coalesce.  The  whole  eye  has  a 
glazed  or  varnished  appearance,  but  lacks  the  lighter  color  shown  by  rugose.  It 
appears  in  both  sexes.  Glazed  females  are  usually  sterile  and  the  males  have  poor 
viabihty,  making  the  character  less  useful  than  rugose. 

Origin. — Glazed  appeared  slightly  before,  and  independently  of,  rugose.  One  male 
was  found  in  a  mass  culture  (see  Metz,  19l6d,  p.  599). 

Comparison. — (See  under  wax,  below.) 

Wax  (r"). 

Description.— Wax  flies  resemble  glazed,  but  the  eyes  are  more  extremely  affected. 
They  are  of  a  pale  yellowish,  uneven  color,  and  the  ommatidia  are  fused  together, 
or  absent,  so  that  the  surface  of  the  eye  has  a  waxy  appearance.  The  eyes  are  con- 
siderably reduced  in  size  and  are  narrowed,  leaving  a  white  zone  much  broader  than 
usual  around  the  margin.  In  the  eye  itself  on  the  posterior  side  there  is  often  a 
white  or  cream-colored  patch  resembling  a  vesicle.  Wax,  like  glazed,  appears  in 
both  sexes  and  has  sterile  females. 

Origin.— {Y  1095.)     Three  males  were  found  in  a  stock  bottle  carrying  fused. 

Comparison.— In  appearance  wax  and  glazed  both  resemble  the  sex-linked  char- 
acter "lozenge"  in  D.  melanogaster.    The  eye  of  lozenge  more  nearly  approaches 


20 


Linkage  Group  I. 


glazed  in  structure,  but  it  is  more  like  wax  in  shape,  and  has  a  bushy  appearance, 
due  to  heavy  black  hairs  or  clusters  of  hairs  on  the  surface.  Lozenge  females  appear 
to  be  partly  sterile,  but  do  not  show  such  a  high  degree  of  sterility  as  do  those  of 
glazed  and  wax.  An  allelomorph  of  lozenge — lozenge-2 — bears  a  close  resemblance 
to  wax  in  appearance,  and  probably  had  sterile  females,  according  to  information 


Fig.  5.— Cut. 
Droop  (d).     (Figure  G.) 


furnished  us  by  Dr.  Sturtevant  and  Dr. 
Bridges.  The  stock  of  lozenge-2  has  been 
lost,  however,  and  we  have  not  been  able 
to  compare  specimens  with  those  of  wax. 
Description. — The  wings  of  droop  flies 
curve  downward  or  droop  at  the  ends. 
The  character  usually  appears  in  both 
wings,  but  sometimes  appears  only  in  one 
or  fails  to  appear  at  all. 


Fig.  6. — Droop.     (Legs    are    normal, 
not  short,  as  indicated.) 


Origin. — (E  780.)  14  droop  males  were  obtained  from  a  pair  mating  of  scaly 
flies,  indicating  that  the  mother  was  heterozygous  for  droop. 

Comparison. — In  appearance  droop  resembles  the  sex-linked  character  "depressed" 
in  D.  melanogaster  (Morgan  and  Bridges,  1916,  p.  67),  but  differs  from  the  latter  in 
being  inconstant. 


Linkage  Data.  21 

LINKAGE  IN  GROUP  I,  AND  CONSTRUCTION  OF 
X-CHROMOSOME  MAP. 

(Figure  7.) 

In  a  previous  paper  (Metz,  1918)  the  linkage  of  the  8  characters 
yellow,  frayed,  vesiculated,  hairy,  magenta,  forked,  rugose,  and 
glazed  was  considered,  and  a  "chromosome  map"  constructed  with 
the  genes  placed  in  the  order  given.  Two  of  the  genes  were  ' '  located ' ' 
only  provisionally — frayed  because  the  stock  was  lost,  and  hairy 
because  of  insufficient  data.  The  position  of  frayed  (with  reference 
to  yellow)  remains  uncertain;  but  that  of  hairy  is  now  known  to  be 
to  the  "left"  (i.  e., above)  instead  of  to  the  right  of  magenta  (Wein- 
stein,  1920,  and  present  data).  Weinstein  (1.  c.)  has  "located" 
the  gene  for  the  character  crossveinless  at  17.6,  or  about  2  units 
to  the  left  of  vesiculated. 

In  the  present  paper  the  genes  for  the  new  characters  are  "located" 
with  reference  to  those  already  known,  and  additional  data  are  given 
on  several  of  the  latter.  Unless  otherwise  specified  the  new  data  in 
the  tables  include  only  the  male  offspring  from  the  various  matings. 

In  this  connection  we  would  emphasize  the  fact  that  we  have  made 
no  attempt  to  carry  out  a  detailed  and  exhaustive  study  of  linkage, 
even  in  the  sex-linked  group  of  characters.  This  would  represent  a 
separate  study,  aside  from  the  purpose  of  the  present  work,  and  one 
which  can  be  carried  out  much  better  after  more  mutant  characters 
are  obtained.  It  will  be  noted,  therefore,  that  numerous  experiments 
which  would  be  of  value  for  a  critical  study  have  not  yet  been  made. 

Since  chromosome  "maps"  are  now  usually  placed  vertically, 
instead  of  horizontally,  on  the  page,  the  terms  "above"  and  "below" 
are  here  used  in  place  of  "left"  and  "right,"  respectively. 

The  data  from  linkage  experiments  on  sex-linked  characters  are 
given  in  full  on  pages  78  to  88  (experiments  1  to  53)  and  are  summar- 
ized in  table  2.  These  are  arranged  according  to  the  number  of  genes 
concerned  and  the  order  of  the  loci  on  the  chromosome  map,  beginning 
with  the  "zero  end."  Thus  the  first  experiments  are  those  involving 
2  pairs  of  genes,  then  those  involving  3  pairs,  and  so  on;  and  in  each 
series  the  uppermost  loci  are  considered  first.  The  summary  in 
table  2  includes  the  calculated  cross-over  percentages  for  successive 
regions  in  each  experiment. 

The  present  section  deals  separately  with  the  linkage  data  on 
each  successive  gene,  and  indicates  the  method  and  data  used  in 
"locating"  the  genes  and  constructing  the  map.  The  data  are 
included,  in  summary  form,  in  table  3,  although  not  all  of  the  data 
in  this  table  are  used  in  constructing  the  map.  For  the  latter 
purpose,  an  effort  has  been  made  to  use  the  experiments  considered 
most  reliable,  and  particularly  those  involving  adjacent  loci.     By 


22  Linkage  Group  I. 

consulting  tables  2  and  3  in  connection  with  the  following  consider- 
ations, the  data  on  each  locus  may  be  evaluated  as  they  are  taken  up 
for  treatment.  Table  3  gives  the  data  for  each  gene  in  the  order  of 
treatment,  together  with  the  experiment  number  and  the  number 
of  flies  involved.  The  latter  indicates  the  relative  value  of  the  experi- 
ments in  respect  to  numbers,  and  the  experiment  number  permits 
reference  to  table  2,  which  indicates  the  number  of  genes  involved 
in  the  experiment  and  other  details  that  aid  in  evaluating  it. 

Sepia. 

In  previous  papers  yellow  has  been  placed  at  the  zero-point  on  the  map;  but  sepia, 
as  shown  by  experiment  19  (table  2)  occupies  a  position  "above"  that  of  yellow,  and 
thus  becomes  the  terminal  gene.  Sepia  and  yellow  give  approximately  5.6  per  cent 
crossing-over,  placing  yellow  at  about  6. 

Yellow. 

Yellow  is  one  of  the  most  frequently  used  characters,  and  its  locus  has  served  as 
a  base  in  numerous  experiments,  as  shoAVTi  by  table  3.  Its  relation  to  sepia  has  been 
considered  under  sepia  (experiment  19).  This  placed  yellow  at  5.6  units  from  sepia. 
With  crossveinless  it  averaged  18.7  per  cent  crossing-over,  with  vermilion  19.6  per 
cent  and  with  vesiculated  18.8  per  cent.  All  of  the  latter  three  values  should  be 
increased  slightly  by  correction  for  double  crossing-over. 

Frayed. 

Frayed  was  only  used  in  three  experiments  before  the  stock  was  accidentally  lost. 
One  of  these  (experiment  2)  was  with  forked.  It  gave  almost  48  per  cent  of  crossing- 
over,  showing  that  the  frayed  locus  is  remote  from  that  of  forked.  Another  was 
with  yellow  (experiment  1,  Metz,  1918)  and  indicated  very  close  linkage  (1.3  per 
cent  crossing-over).  The  third  was  with  vesiculated  and  magenta  (experiment  14, 
Metz,  1918)  and  indicated  a  locus  about  18  units  to  the  left  of  vesiculated.  On  the 
basis  of  these,  frayed  is  tentatively  placed  1  unit  below  yellow.  That  it  is  close  to 
yellow  is  clear,  but  it  is  possible  that  the  position  should  be  above  rather  than  below 
that  of  yellow. 

Crossveinless. 

Weinstein  (1920)  has  placed  crossveinless  at  17.6  units  to  the  right  of  (or  below) 
yellow.  Our  data,  summarized  in  table  3,  give  a  value  of  19.6  units  for  this  "region," 
based  on  3,093  flies,  without  correction  for  double  crossing-over.  The  value  of  18.7 
per  cent  used  for  calculating  map  length  is  based  on  the  combined  data  (5,450  flies). 
By  adding  this  18.7  per  cent  to  the  5.6  per  cent  given  by  sepia  and  yellow,  the  value 
24.3  per  cent  is  obtained.  Expressed  in  round  numbers,  this  gives  crossveinless  a 
locus  at  24  on  the  map. 

Vermilion. 

Preliminary  tests  indicated  that  vermilion  was  very  closely  linked  to  crossveinless, 
and  experiments  20,  36,  and  46,  involving  yellow,  crossveinless,  and  vermilion,  placed 
vermilion  slightly  below  crossveinless.  The  average  of  all  data  (table  3)  gives  a 
cross-over  value  of  about  0.47  per  cent  between  the  two.  This  would  place  vermilion 
between  crossveinless  and  vesiculated,  although  the  sum  of  our  crossveinless-ver- 
milion  and  vermilion-vesiculated  values  does  not  agree  very  closely  with  the  cross- 
veinless-vesiculated  value  (1.2  per  cent)  obtained  by  Weinstein  (1920).  Our  tests  of 
vermilion  with  vesiculated  (table  3)  give  a  value  of  approximately  2  units. 

The  exact  value  depends  upon  how  the  data  are  treated.  If  all  the  flies  are 
counted  the  result  is  2  per  cent.    But  since  vesiculated  occasionally  fails  to  appear 


Linkage  Data.  23 

(i.  e.,  overlaps  normal),  this  value  is  probably  not  accurate.     When  only  vesiculated 
flies  are  considered  the  value  becomes  1.7  per  cent. 

In  either  case  this  value,  plus  the  crossveinless-vermilion  value  of  0.47  unit,  con- 
siderably exceeds  the  crossveinless-vesiculated  value  of  1.2  units  obtained  by  Wcin- 
stein,  which  suggests  that  the  above  sequence  of  loci  may  be  incorrect.  To  test  this 
possibility  an  experiment  involving  all  three  genes  (crossveinless,  vermilion,  and 
vesiculated)  together  was  carried  out. 

Vesiculated. 

The  results  of  this  experiment  (see  last  paragraph)  make  it  practically  certain 
that  the  sequence  is  as  given  above,  i.  e.,  crossveinless-vermilion-vesiculated  (see 
experiment  36,  p.  81).  The  conclusion  is  warranted  in  spite  of  the  fact  that  two  of 
the  cross-over  classes  contain  only  one  fly  each,  for  one  of  these  is  critical.  It  is  the 
one  in  the  crossveinless-vermilion-vesiculated  class.  The  presence  of  this  fly  rule* 
out  the  order  vermilion-crossveinless-vesiculated  because  it  would  involve  a  double 
cross-over  within  a  "distance"  of  less  than  3  units.  Likewise  the  order  crossveinless- 
vesiculated-vermilion  is  ruled  out  by  the  large  number  of  vermilion  flies  and  of  yellow- 
cross  veinless- vesiculated  flies,  which  would  also  require  double  cross-overs  in  this 
short  region.  The  proper  order,  therefore,  appears  to  be  crossveinless,  vermilion, 
vesiculated,  unless  an  error  was  made  in  classification,  which  seems  very  unlikely. 

The  map  locus  of  vesiculated  is  calculated  by  using  that  of  crossveinless  as  a  base 
and  adding  the  crossveinless-vermilion  and  vermilion-vesiculated  values.  These  are, 
respectivelj'^,  0.5,  and  1.7,  giving  a  total  of  2.2,  of  a  map  locus  of  26. 

Singed. 

Singed  has  been  tested  with  vermilion,  crossveinless,  and  yellow  in  the  one  direc- 
tion, and  with  magenta,  forked,  triangle,  and  others  in  the  opposite  direction  (table  3). 
Experiment  21,  involving  yellow,  crossveinless,  and  singed,  gives  singed  a  position 
about  17  units  below  crossveinless  and  makes  clear  the  order  of  the  genes.  This  is 
verified  by  experiments  25  and  41,  involving  yellow,  singed,  and  short  in  the  one 
case,  and  vermilion,  singed,  magenta,  and  forked  in  the  other.  The  best  available 
data  for  locating  singed  are  provided  by  experiments  involving  vermilion  or  cross- 
veinless on  the  one  side  (experiments  6,  21,  34,  41,  48)  and  magenta  forked  on  the 
other  (experiments  41,  45,  48).  The  crossveinless-singed  value  is  15.7,  and  the 
vermilion-singed  value  is  17.9.  The  former  value  is  probably  too  low,  due  to  the 
inclusion  of  experiment  48,  which  appears  to  give  low  values  in  the  upper  part  of 
the  map  (i.  e.,  the  sepia-crossveinless  value  is  only  18.7,  and  the  crossveinless-singed 
value  only  14).  On  this  account,  and  also  because  the  vermilion-singed  value  is 
based  on  a  larger  count,  the  latter  is  used  in  constructing  the  map.  It  places  singed 
at  43.0.  Tests  with  magenta  and  forked  are  considered  in  the  discussion  of  the  latter 
characters. 

Oblique. 

Oblique  was  obtained  too  late,  to  permit  of  the  data  on  its  linkage  relatioca  being 
included  in  the  tables  of  summaries,  hence  they  will  be  considered  fully  here.  The 
approximate  location  of  oblique  on  the  chromosome  map  was  determined  by  means 
of  two  small  experiments  involving,  respectively,  magenta,  forked,  oblique,  and  short 
(experiment  49)  and  sepia,  crossveinless,  oblique,  and  short  (experiment  50).  In  the 
latter  only  the  not-oblique  flies  are  used  in  the  calculation,  because  oblique  interferes 
with  the  classification  of  both  sepia  and  crossveinless.  The  values  obtained  in  these 
two  experiments  indicated  that  oblique  was  between  crossveinless  and  forked,  so 
matings  were  made  to  test  its  Hnkage  T\ith  singed,  which  has  a  locus  intermediate 
between  these  two.  The  results  of  the  tests  with  singed  are  given  in  experiments  51, 
52,  and  53.    The  first  of  these  shows  that  oblique  falls  very  close  to  singed  (2  cross- 


24  Linkage  Group  I. 

overs  in  48  flies),  and  the  other  two  agree  in  giving  it  a  position  approximately  6 
units  above  that  of  singed.  In  both  of  the  latter  a  difficulty  in  classification  arises 
through  the  presence  of  oblique  and  sepia  together.  This  necessitates  omitting  the 
oblique  flies  from  the  calculation  or  else  apportioning  them  between  the  oblique  and 
the  oblique  sepia  classes.  Both  methods  are  used,  and  the  results  are  in  such  close 
agreement  as  to  cause  no  difficulty  in  estimating  the  approximate  values. 

The  map  location  of  oblique  has  been  calculated  from  the  average  of  the  three 
experiments  just  considered.  When  only  the  not-oblique  flies  are  used  (in  the  last 
two  cases)  the  result  is  11  cross-overs  in  186  flies,  or  a  value  of  5.9  per  cent.  When 
all  flies  arc  used  the  result  is  15  cross-overs  in  263  flies,  or  a  value  of  5.7  per  cent;  6 
per  cent  is  therefore  used  as  the  approximate  value  in  constructing  the  map,  and 
oblique  is  placed  6  units  above  singed.  It  should  be  noted,  however,  that  in  both 
of  the  experiments  involving  sepia,  the  sepia-singed  value  is  unusually  low,  ranging 
around  19  instead  of  about  40,  as  it  should.  The  singed-short  value,  on  the  other 
hand,  agrees  approximately  with  expectation.  This  suggests  that  in  these  experi- 
ments a  factor  was  present  which  reduced  crossing-over  in  the  "upper  end"  of  the 
chromosome.     If  so,  the  locus  of  oblique  may  be  placed  too  close  to  that  of  singed. 

Hairy. 

Hairy  has  been  used  very  little  in  Unkage  tests  because  of  its  unsatisfactory  nature. 
In  a  test  with  forked  (Metz,  1918)  it  gave  about  3  per  cent  crossing-over,  Weinstein 
(1920)  found  it  to  be  at  the  "left"  of  (above)  magenta,  and  obtained  a  cross-over 
value  of  5.4  per  cent  with  magenta.  Our  experiments  26,  28,  29,  37,  and  42  indicate 
the  same  sequence  of  genes  and  give  very  nearly  the  same  cross-over  value  \vith 
magenta  (5  per  cent).  The  combined  data  give  a  value  of  5.3  per  cent,  placing  it 
at  about  62  of  the  map. 

Magenta  and  Forked. 

Since  magenta  and  forked  have  been  used  in  combination  almost  exclusively, 
they  may  be  considered  together.  They  were  among  the  first  sex-linked  characters 
obtained  and  have  been  used  extensively  ever  since.  The  order  of  their  genes  with 
reference  to  the  other  principal  loci  is  indicated  by  previously  published  data  and 
by  experiments  27,  29,  30,  31,  37,  and  40  to  48.  The  cross-over  value  of  the  magenta- 
forked  region  is  the  best  known  one  in  D.  virilis.  The  data  of  Metz  (1918)  give  a 
value  of  3.7  units,  based  on  2,529  flies  and  those  of  Weinstein  (1920)  give  a  value  of 
4  per  cent  based  on  1,642  flies.  Data  in  the  present  paper  (table  3)  give  3.4  units, 
based  on  6,208  flies.  Combined  these  give  a  value  of  3.6  units,  which  is  used  in 
constructing  the  present  map. 

Magenta  and  forked  are  located  with  reference  to  singed  by  using  the  singed- 
magenta  value  of  25.1  units  given  by  experiments  41,  45,  and  48  (table  3).  This 
places  magenta  at  about  67  and  forked  at  about  71  units  from  the  zero  end  of  the 
map.  These  loci  should  be  placed  more  accurately  by  obtaining  large  numbers  in 
an  experiment  involving  vermilion  (or  crossveinlcss),  singed,  magenta,  and  forked 
simultaneously.  Our  experiments  41  and  48  are  of  this  nature,  but  the  counts  only 
include  718  flies. 

Triangle  and  Short. 

Triangle  is  shown  by  experiments  13  and  32  to  be  closely  linked  to  short.  The 
latter  character  appeared  later,  chronologically,  than  triangle,  but  is  much  better  for 
linkage  studies  and  consequently  is  used  more  than  triangle.  The  average  cross-over 
value  between  the  two  (table  3)  is  5.1  per  cent.  Experiment  32  shows  that  the 
position  of  short  is  between  that  of  triangle  and  droop,  and  experiment  33  shows 
that  it  is  above  rugose. 

In  locating  triangle  and  short  on  the  map,  four  different  lines  of  evidence  have 
been  considered,  as  summarized  on  the  following  page. 


Linkage  Data. 


25 


I. 

II. 

III. 

IV. 

f 

f-T 
T 

T-8 

B 

B-r 

r 

r-d 

d 

71.1 
10.7  (269) 

f 
f-r 

r 
8-r 

8 
T-8 

T 

71.1 

26.3  (3.727) 

si     42.4 
8i-8     42.9(1.442) 

f     71.1 

f-8     18.5  (677) 

81.8 
6.1  (607) 

97.4 
16.9 

86.9 

15.9  (1,664) 

a     85.3 
T-8       5  1 

8     89.6 
T-8       5.1 

81.5 
5.1 

102.8 
7.2  (470) 

T     80.2 

B     85.3 
B-r     15.9 

T  84.6 

76.4 

110 

r  101.2 

By  adding  the  successive  values  from  forked  (i.  e.,  f-T+T-s),  triangle  comes  at 
81.8  and  short  at  86.9.  Neither  of  these  is  based  on  large  numbers,  however,  and 
consequently  they  are  open  to  question.  The  second  method  involves  the  use  of 
the  singed-short  value,  which  is  based  on  1,442  flies.  This  would  place  short  at  85.3, 
which  differs  by  less  than  2  units  from  the  other  value.  By  working  back  from  this, 
triangle  would  be  placed  at  80.2.  In  contrast  to  these  two  lines  of  evidence,  which 
give  essentially  the  same  results,  the  other  two  deviate  considerably,  and  in  opposite 
directions.  The  first  is  based  on  the  forked-short  value  as  given  by  experiments  45 
and  48  (577  flies).  These  experiments  are  particularly  significant,  because  both 
involve  singed,  magenta,  forked,  and  short  simultaneously.  According  to  these,  the 
forked-short  distance  is  18.5,  placing  short  at  89.6,  or  3  units  beyond  the  more  extreme 
of  the  two  values  given  above. 

The  fourth  method  considered  is  that  of  using  the  forked-rugose  value  to  locate 
rugose  (at  97.4)  and  then  working  backward  to  locate  short  and  triangle.  This 
places  short  at  81.5  and  triangle  at  76.4,  about  4  units  less  than  the  least  extreme 
value  given  above.  Since  the  forked-rugose  value,  upon  which  these  depend,  is  prob- 
ably too  short  by  about  this  amount,  due  to  undetected  double  crossing-over,  it  seems 
probable  that  the  first  two  methods  give  approximately  correct  results.  They  also 
represent  roughly  the  average  of  the  other  values,  and  hence  they  are  used  in  con- 
structing the  map.  Triangle  is  thus  placed  at  81  (intermediate  between  80.2  and  81.8) 
and  short  at  86  (intermediate  between  85.3  and  86.9). 

Cut. 

As  noted  above,  cut  appeared  in  a  culture  carrying  short,  and  has  behaved  like  an 
allelomorph  of  short.  The  original  female,  heterozygous  for  cut,  and  either  hete- 
rozygous or  homozygous  for  short,  gave  23  cut  and  26  short  sons,  wth  no  wild-type 
or  cut  short  sons.  The  daughters  were  all  wild-type.  Nine  of  these  were  tested 
individually  and  proved  to  be  of  two  types;  4  of  them  gave  short  sons  and  sons  with 
normal  wings,  but  no  cut,  and  5  of  them  gave  cut  sons  and  sons  with  normal  wings, 
but  no  short  (M  182,  197,  204,  206-209,  232,  234).  Females  heterozygous  for  cut 
and  carrying  short  in  the  opposite  X-chromosome  have  been  used  in  keeping  the 
stock  of  cut,  and  their  sons  have  thus  far  been  of  the  two  types  short  and  cut. 


D.  H.  HILL  LIBRARY 


KI^Np-fk*    I     •r>t-/^lir«  r»    vfaffa   I 


nWe^ne^ 


26  Linkage  Group  I. 

Rugose,  Glazed,  and  Wax. 

Since  rugose  is  the  best  of  these  three  allelomorphs  for  use  in  linkage  experiments, 
the  present  data  are  nearly  all  based  on  this  character.  These  are  summarized  under 
experiments  9,  14,  16,  18,  33,  35,  38,  39,  43,  44,  and  47.  The  locus  of  rugose  is 
placed  on  the  map  on  the  basis  of  the  short-rugose  value  of  15.9,  which  gives  rugose 
a  position  at  102,  based  on  1,564  flies.  This  is  about  4  units  beyond  the  position 
given  by  using  the  forked-rugose  value,  but  is  believed  to  be  more  accurate  than  the 
latter,  since  it  eliminates  most  of  the  undetected  double  cross-overs. 

Droop. 

Droop  has  been  used  in  experiments  with  singed,  magenta,  forked,  triangle,  short, 
and  rugose  (table  3).  These  agree  in  indicating  that  its  locus  is  in  the  lower  part  of 
the  map,  and  experiments  32  and  33  show  that  it  falls  beyond  rugose,  which  has 
previously  marked  the  extreme  end  of  the  map.  Its  position  is  determined  with 
reference  to  rugose  by  experiments  18  and  33,  which  place  it  7.2  units  from  rugose, 
or  at  approximately  109. 


Linkage  Data. 


27 


Table  2. — Summary  of  linkage  experiments  on  sex-linked  characters. 


Experi- 
ment 
No. 


Genes  involved. 


Cross-over  percentage. 


Total 
flies. 


1 

2 

3 

4 

5 

5 

6 

7 

8 

9 

10 

11 

12 

12 

13 

14 

15 

16 

17 

17 

18 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 
30 

31 

32 
33 

34 
35 
36 

37 
38 

39 

40 
41 
42 

43 
44 
45 
46 
47 

48 


se-v 

fd-f 

y-c 

y-v 

v-vs 

V-V8 

v-si 

V-8 

v-T 

v-r« 

si-T 

si-B 

ei-d 

si-d 

T-8 

T-r 
T-d 

e-r 

e-d 

6-d 

r-d 

r-d 

se-y-c 

y-c-v 

y-c-si 

y-c-8 

y-c-d 

y-v-s 

y-si-8 

y-ha-m 

v-m-f 

vs-ha-m 

ha-m-f 
m-f-T 

m-f-d 

T-s-d 
8-r-d 

se-c-si-s 
se-c-s-r 
y-c-v-vs 

y-ha-m-f 
y-vs-f-r 

y-vs-f-r* 

c-v-m-f 
v-si-m-f 
vs-ha-m-f 

v8-m-f-r 

si-m-f-s 

y-c-v-m-f 

y-vs-m-f-r 

Be-c-si-m-f-8 


se-v 
fd-f 
y-c 
y-v 

V-V8 

v-va 
v-si 

v-8 

V-T 

v-r« 

si-T 

si-s 

si-d 

si-d 

T-s 

T-r 

T-d 

s-r 

B-d 

B-d 

r-d 

r-d 

se-y 

y-c 

y-c 

y-c 

y-c 

y-v 

y-si 

y-ha 

v-m 

v8-ha 

vs-ha 

ha-m 

m-f 

m-f 

T-s 

s-r 

se-c 
se-c 
y-c 

y-ha 

y-vs 

y-vs 

y-vs 

y-vs 

c-v 

v-si 

vs-ha 

vs-ha 

vs-m 

vs-m 

si-m 

y-c 

y-vs 

y-vs 

se-c 


23.5. 

47.6. 

21.2. 

20.6. 

2.4, 

1.9. 

18.6. 

43.2. 

38.9. 

42.5. 

39.7. 

39.2. 

46.2, 

41.3. 

5.5. 

8.9. 

23.6, 

18.2. 

28.0 

14.3 

13.2 

7.5 

5.6 

20.3 

17.0 

17.5 

20.2 

14.2 

34.1 

41.3 

31.5 

39.6 

41.8 

3.6 

0.7 

2.5 

4.8 
13.2 

21.9 
20.0 
20.7 

48.8 
21.1 

7.1 
17.9 
18.3 

0.4 
16.3 
30.9 
19.8 
33.7 
32.8 
28.6 
18.3 
20.8 
21.2 
18.7 


counting  all  flies 

counting  only  vs  flies. 


counting  all  flies.  . . . 
counting  only  d  flies. 


counting  only  d  flies. 


counting  all  flies 

counting  only  d  flies 

counting  all  flies 

counting  only  d  flies 

y-c  20. 8 

c-v  0.4 

c-si  16.8 

c-8  44 . 5 

c-d39.2 

V-S37.3 

si-s  33. 5 

ha-m  4.8 

m-f  3.6 

ha-m  3.3,  counting  all  flies. 

counting  only  vs  flies 

m-f  1.8 

f-T  10.7. 

f-T    3 . 7,  counting  only  T  flies . 
f-d  38.5,  counting  all  flies, 
f-d  25.0,  counting  only  d  flies, 
s-d  20.6. 

r-d  21 .3,  counting  all  flies 

r-d     6 . 7,  counting  only  d  flies 

c-si  17 . 7.  si-s  39 . 0 

c-s  44.2.  s-r  14.8 

c-v    0 . 5.  v-vs  1 . 0,  counting  all  flics 

v-vs  1.1,  counting  only  vs  flies 

ha-m  5.4,  m-f  4.9 

vs-f  40. 1,  f-r  28.8.  counting  all  flies 

vs-f  47. 1,  counting  only  vs  flies 

vs-f  32.4,  f-rK  35.5,  counting  all  flics 

vs-f  45.9,  counting  only  vs  flies 

v-m  36.9,  m-f  1.9 

si-m  19 . 2,  m-f  5.1 

ha-m  6.9,  m-f  2.3,  counting  all  flies 

counting  only  vs  flies 

m-f  5.2,  f-r  26.0,  counting  all  flies 

counting  only  vs  flies 

m-f  4.1,  f-s  19.8 

c-v  0.6,  v-m  35  0,  m-f  2.0 

vs-m  31.6,  m-f  4.7,  f-r  27.2,  counting  all  flies. 

vs-m  43.2,  counting  only  vs  flies 

c-si  14.0,  si-m  28.0,  m-f  3.2.  f-s  17.9 


645 
254 
406 
432 
967 
472 
802 
1653 
167 
200 
136 
651 

80 

29 
292 
168 

72 
730 
196 

56 
688 
306 
648 
472 
417 
137 

79 
225 
173 

63 
165 
121 

55 
166 
269 
135 
161 

64 
315 
409 
164 
141 
425 
395 
176 
223 
142 

70 
478 
207 
1411 
312 
217 

96 
1708 
830 
171 
639 
360 
141 
408 


28 


Linkage  Group  I. 


Table  3. — Summary  of  linkage  data  on  sex-linked  genes  arranged  according  to  map  order. 


Region. 

Experiment  No.' 

Total  flies. 

1 

Cross- 
overs. 

Average 
per  cent. 

se-y 
y-fd 
y-o 

y-v 
y-v8 

fd-ve 

19   

548 

31 

5.6 
1.3 

18.7 
19.6 

18.8 
18.5 

1  (Metz,  1918)... 

1,2,3  (Weinstein, 
1920) 

3 

308 

4 

2,357 

415 

406 

86 
114 
96 
71 
24 
16 
82 
117 

19 

548 

20 

472 

21 

417 

22   

137 

23   

79 

36 

395 

46 

639 

Total 

Grand  total . . 
4 

3,093 

606 

5,450 

1,021 

432 

89 
98 
32 

84 
121 

20 

472 

24 

225 

36 

395 

46   

639 

Total 

2  (Metz,  1918)..  . 

6  (Metz,  1918)... 

7  (Metz,  1918)... 
9  (Metz,  1918)... 

16  (Metz,  1918)... 

17  (Metz,  1918)... 

18  (Metz.  1918)... 

19  (Metz,  1918)... 
1,  4,  (Weinstein, 

1920) 

Total 

36 

2,163 

424 

151 

35 
41 
32 
92 

183 
47 

120 
71 

495 

187 

187 

579 

1,086 

298 

699 

361 

2,473 

6,021 

1,116 

88 

(36) 
30 

(5) 
86 

(38) 
75 

(30) 

279 

395,  counting  all  flies 

38 

(176,  counting  only  vs  flies). 
142,  counting  all  flies 

39 

(70,  counting  only  vs  flies) . 
478,  counting  all  flies            . . . 

47 

(207,  counting  only  vs  flies) . 
360.  countine  all  flies 

Total 

Grand  total.. 
14  (Metz,  1918)... 

(141,  counting  only  vs  flies). 

1 ,375,  counting  all  flies 

7 ,  396,  counting  all  flies 

1,395 

296 

55 

'  Except  where  otherwise  specified  the  experiment  numbers  refer  to  experiments  in  the  present 
paper. 


Linkage  Data. 


29 


Table  3. — Summary  of  linkage  data  on  sex-linked  genes  arranged  according  to  map 

order — Continued. 


Region. 

Experiment  No, 

Total  flies. 

Cross- 
overs. 

Average 
per  cent. 

c-v 

C-V8 

v-vs 

c-si 

v-si 
si-m 

ei-f 

si-T 

si-s 

vs-m 

20 

472 

2 
2 
6 
4 

0.47 
1.2 

1.7 

16.7 

17.9 
25.1 

29.1 
39.7 

42.9 

36 

395 

40 

1,411 

46 

639 

Total 

1  (Weinstein, 

1920) 

36 

2,917 

14 

1 , 560 

18 
6 

(3) 

24 

395,  counting  all  flies 

Grand  total . . 
6 

(176,  counting  only  vs  flies). 

1 ,955,  counting  all  flies 

(967,  counting  all  flies) 

472,  counting  only  va  flies 

(23) 
9 

(4) 
2 

36 

(395,  counting  all  flies) 

176,  counting  only  ve  flies 

Total 

21 

648,  counting  only  vs  flies 

11 

417 

70 
25 
57 

34 

141 

48 

406 

Total 

6 

964 

152 

802 

149 
51 

41 

312 

Total 

41 

1,114 

200 

312 

60 

49 

114 

45 

171 

48 

406 

Total 

41 

889 

223 

312 

76 

56 

127 

45 

171 

48 

406 

Total 

10 

889 

259 

136 

54 

11 

551 

216 

68 

66 

.  .      90 

25 

173 

34 

141 

45 

171 

48 

406   

200 

Total 

3  (Metz,  1918)... 
7  (Metz,  1918).  .  . 

11  (Metz,  1918)..  . 

12  (Metz,  1918)..  . 
14  (Metz,  1918).  .  . 
16  (Metz,  1918)... 
19  (Metz,  1918)... 

Total 

1,442 

619 

263   

85 
57 
138 
190 
106 
368 
107 

187   

463   

504 

296     

1 , 086   

361    

3,160   

1.051 

30 


Linkage  Group  I. 


Table  3. — Summary  of  linkage  data  on  sex-linked  genes  arranged  according  to  map 

order — Continued. 


Region. 

Experiment  No. 

Total  flies. 

Cross- 
overs. 

Average 
per  cent. 

ha-m 
m-f 

f-T 

28   

121,  counting  all  flies 

52 

(24) 
82 

(21) 
576 

(275) 
114 

(61) 

824 

33.6 
5.3 

3.8 
10.7 

42   

(55,  counting  only  vs  flies) . 
217,  counting  all  flies      .      .    . 

43\ 

(96,  counting  only  vs  flies) . 
1,708,  counting  all  flies. 

44 1 

(830,  counting  only  vs  flies) . 
360,  counting  all  flies 

47 

Total 

Grand  total . . 

3,  4,  5  (Weinstein, 
1920) 

26 

(141,  counting  only  vs  flies). 

2 ,  406,  counting  all  flies 

5,566 

1,875 

1,388 

76 

63 

3 
4 
6 

12 
15 

28 

121 

29 

166 

37 

223 

42 

217 

Total 

Grand  total. . 

3  (Metz,  1918)... 

5  (Metz,  1918)... 
12  (Metz,  1918)... 
16  (Metz,  1918) .  . . 

2,  4   (Weinstein, 
1920) 

Total 

27 

790 

40 

2,178 

116 

262 

13 
17 
23 

42 

66 

677 

504 

1,086 

1,642 

4,171 

161 

165 

6 

29 

166 

3 
2 

4 
11 
28 
16 

5 

89 

7 
13 
17 
13 

30 

269 

31 

161 

37 

223 

40 

1,411 

41 

312 

42 

217 

431 

1,708 

44/ 

45 

171 

46 

639 

47 

360 

48 

406 

Total 

Grand  total. . 
30 

6,208 

214 

10,379 

375 

269,  counting  all  flies 

29 

(5) 

(135,  counting  only  T  flies). 

Linkage  Data. 


31 


Table  3. — Summary  oj  linkage  data  on  sex-linked  genes  arranged  according  to  map 

order — Continued. 


Region. 

Experiment  No. 

Total  flies. 

Cross- 
overs. 

Average 
per  cent. 

f-8 

f-r 
f-d 

T-8 

T-r 
T-d 

3-r 

8-d 

r-d 

46 

171 

406 

34 
73 

18.5 

26.3 
25.0 

6.1 
8.9 

25.7 

15.9 

17.7 
7.2 

48 

Total 

4  (Metz,  1918) . . . 
13  (Metz,  1918) . . . 
18  (Metz,  1918) . . . 

2  (Weinstein, 
1920) 

Total 

38 

577 

107 

286 

81 

47 

193 

74 

173 

699 

359 

1,517 

395 

142 

41 
445 

98 

431 

1,708 

44/ 

47 

360 

Total 

Grand  total. . 
31 

2,210 

684 

3,727 

979 

(161,  counting  all  flies) 

64,  counting  only  d  fliea 

(62) 
16 
16 
15 

13 

292 

32 

315 

Total 

14 

607 

31 

168 

15 

15 

72,  counting  only  d  flies 

17 

(80) 
42 

32 

(315,  counting  all  flies) 

157,  counting  only  d  flies 

Total 

16 

229,  counting  only  d  fliea 

59 

730 

133 
54 
63 

33 

409 

35 

425 

Total 

17 

1 , 564 

250 

(55) 
8 
(65) 
33 

(141) 
26 

(196,  counting  all  flies) 

66,  counting  only  d  flies 

32 

(315,  counting  all  flies) 

157,  counting  only  d  flies 

33 

(409,  counting  all  flies) 

164,  counting  only  d  flies 

Total 

18 

377,  counting  only  d  flies 

67 

306,  counting  only  d  flies 

23 
11 

33 

164,  counting  only  d  flies 

Total 

470,  counting  only  d  flies 

34 

32  Linkage  Group  II. 

III.  LINKAGE  GROUP  II. 

Since  confluent  was  the  first  non-sex-linked  character  found  in 
D.  virilis,  the  group  to  which  it  belongs  is  designated  Group  II. 
It  consists  of  the  four  characters  confluent,  concave,  double,  and 
broken.  The  first  two  are  excellent  characters  and  have  been  used 
extensively;  the  third  is  very  poor  for  linkage  work  and  has  been  used 
relatively  little;  while  the  last,  although  a  good  character,  appeared 
so  recently  that  it  has  been  possible  to  use  it  only  in  preliminary 
experiments. 

DESCRIPTION,  ORIGIN,  AND  COMPARISON  OF 
CHARACTERS  IN  GROUP  II. 

Confluent  (C).     (Plate  3,  Figure  1.) 

Description. — Confluent  derives  its  name  from  the  fact  that  the  second  vein  is  con- 
fluent with  the  costal  vein  for  a  short  distance  near  the  tip  of  the  latter,  as  showTi  in 
the  figure  (also  Metz,  1916,  fig.  2).  The  fly  appears  to  be  unaffected  otherwise,  save 
for  a  thickening  of  the  outer  ends  of  the  two  cross-veins,  and  a  slight  roughening  of 
the  eyes  in  most  cases.  Confluent  resembles  the  extreme  form  of  the  sex-linked 
character  triangle,  and  like  the  latter  is  dominant.  Unlike  triangle,  however,  it  is 
lethal  in  the  homozygous  condition  and  pure  stock  can  not  be  obtained.  In  combi- 
nation with  the  other  dominant  wing  characters,  branched,  net,  and  extra,  confluent 
is  exaggerated,  the  confluence  of  the  second  and  costal  veins  being  more  extended. 
It  is  likewise  exaggerated  by  capsule,  as  noted  under  the  description  of  the  latter. 

Origin. — Confluent  was  one  of  the  first  characters  found  in  D.  virilis  (see  Metz, 
1916,  p.  593). 

Comparison. — Confluent  resembles  the  "confluent"  of  D.  melanogaster  in  appear- 
ance and  in  being  a  dominant.  It  is  probable  that  they  agree  also  in  being  lethal 
when  homozygous  (see  Metz,  1916,  p.  591,  and  Morgan,  Bridges,  and  Sturtevant, 
1919,  p.  257). 

Concave  (cc).     (Plate  3,  Figures  3  to  7.) 

Description. — The  principal  diagnostic  characters  of  concave  are  the  curled,  instead 
of  straight,  hairs  on  the  arista  (fig.  4,  plate  3),  and  the  heavy,  somewhat  wa\y  bristles 
on  the  scutellum.  The  former  is  constant  and  definite  and  the  latter  is  usually  evident. 
In  addition  the  scutellar  bristles  frequently  stand  erect  or  point  in  various  directions, 
the  dorso-central  bristles  sometimes  are  similarly  affected,  the  posterior  scutellar  bristles 
extend  nearly  parallel  instead  of  crossing,  and  often  the  wings  are  abnormal.  The 
latter  effect  is  very  irregular.  Sometimes  both  wings  are  very  small,  or  narrow,  or 
short  and  nearly  circular  (a  common  type),  or  concave  instead  of  convex  on  the  inner 
margin.  Often  only  one  wing  is  affected,  or  the  two  may  be  differently  affected. 
Two  typical  wing  forms  are  shown  in  an  earlier  paper  (Metz,  1916,  figs.  5  and  6). 

Origin. — The  origin  of  concave  is  given  in  the  paper  just  cited. 

Comparison. — Concave  is  paralleled  very  closely  by  the  third  chromosome  re- 
cessive character  "crumpled"  in  D.  melanogaster.  Both  have  the  curled  hairs  on  the 
arista,  and  the  same  type  of  abnormal  scutellar  bristles  and  both  exhibit  a  series  of 
wing  modifications,  of  which  the  most  frequent  types  are  similar  in  the  two  species. 

Double  (de). 

Description. — Double  is  characterized  by  an  occasional  doubling  of  part  of  the 
fourth  vein  or  fifth  vein,  especially  near  the  posterior  cross-vein,  by  the  presence  of  a 
tubercle  on  the  first  vein  in  some  individuals,  and  frequently  by  a  broadening  and 


Description  of  Characters. 


33 


arching  of  the  wing  as  well  as  by  the  angular  position  in  which  the  wing  is  held  out 
from  the  body.  None  of  these  characters  is  constant,  and  for  this  reason  considerable 
difficulty  is  experienced  in  classifying  the  flies.  Owing  to  this  and  to  the  fact  that 
double  flies  have  very  poor  viability,  the  stock  has  been  discarded. 

Origin. — (V  1169.)  Double  first  appeared  in  a  pair  mating,  both  parents  evi- 
dently having  been  heterozygous;  the  offspring  were  57  double  (28  9  9:29cfcr), 
and  190  not  double  (89  9  9  :  101  cf  d^). 

Table  4. — Chronological  list  of  autosomal  characters  in  Drosophila  virilia. 


Character. 


Sym- 
bol. 


Parts 
affected. 


Link- 
age 
group 


First 
observed. 


Found 
by- 


Record. 


Confluent.  .  .  . 
Concave 

Steel 

Acute 

Branched 

Fused 

Telescoped .  .  . 

Scaly 

Double 

Hump 

Minus 

Capsule 

Hunch 

Pinched 

Interrupted . .  . 
Approximated, 
Net 

Spine 

Spread 

Broken 

Garnet 

Extra 

Ruffled 


C 

CO 

St 

ac 
B 
fu 

t 

S 

de 

hp 

mi 

cp 

h 

P 

i 

a 

Nt 

en 
sp 
b 
G 
E 
ru 


Wing  veins .  . 

II 

Bristles    and 

wmgs 

II 

Eyes 

III 

Wings 

IV 

Wing  veins .  . 

V 

Wing  veins .  . 

V 

Thorax 

III 

Eyes 

III 

Wing  veins .  . 

II 

Thorax 

IV 

Bristles 

? 

Wings 

? 

Thorax 

iii 

Wing  veins .  . 

IV 

Wing  vein .  .  . 

V 

Wing  vein .  .  . 

V 

Wing     veins 

and  bristles 

? 

Wing  vein .  .  . 

? 

Wings 

iii 

Wing  vein.  .  . 

II 

Eye  color. .  .  . 

III 

Wing  vein.  .  . 

? 

Thoracic 

hairs  and 

bristles. .  .  . 

V 

July.   1914 

Sept.,  1915 
Feb.,  1916 

Do 
Sept.,  1916 
Nov.,  1916 
Feb.,  1917 
July,   1917 

Do 
Mar.,  1919 

Do 
Apr.,  1919 
May,  1919 
June,  1919 
Sept.,  1919 

Do 

Do 
June,  1920 
Mar.,  1921 
May,  1922 

Do 
June,  1922 


Do 


Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Metz 

Mason 

Mason 

Metz 

M.  Demerec 

Moses 

Moses 

Metz 

Metz 

Metz 


Metz,  1916,  p.  693 


Metz,  1916, 
Metz,  1916, 
c  stock. 

V  601.  606. 

V  778. 
V974. 

V  1128. 

V  1169. 
Hyde  stock. 
L  22. 
L92. 

L  176. 
L252. 
E  15. 
E  15. 

L462. 
P  stock. 
P  577. 
M  66. 
M  13. 
M  21. 


M  113. 


597, 
698, 


Broken  (b).     (Plate  3,  Figures  8  and  9.) 

Description. — The  character  takes  its  name  from  the  break  in  the  cross-veins. 
The  posterior  cross-veins  are  usually  lacking,  but  may  be  broken,  or,  in  rare  cases, 
one  may  be  intact  but  thin  in  the  middle.  The  anterior  cross-veins  are  sometimes 
absent  or  broken,  but  not  constantly  so.  Frequently,  the  distal  end  of  the  third 
and  fourth  veins  is  thin,  and  occasionally  these  veins  fail  to  reach  the  wing-margin. 
In  addition  to  the  effects  on  the  veins,  a  characteristic  soft,  wavy,  and  glossy  appear- 
ance of  the  wing  as  a  whole  may  usually  be  noticed.  In  most  of  the  flies  the  posterior 
cross-veins  are  entirely  gone,  as  they  are  in  crossveinless  flies.  When  this  is  not  the 
case,  the  end  of  the  vein  nearest  the  fourth  vein  is  usually  gone,  resulting  in  a  con- 
dition almost  indistinguishable  from  that  found  in  interrupted  flies  (fifth  chromo- 
some). The  frequency  of  these  types  may  be  judged  roughly  from  the  following 
count  of  50  flies  taken  from  a  stock  bottle:  in  46  specimens  both  posterior  cross-veins 
were  entirely  gone,  in  3  both  posterior  cross-veins  were  broken  (end  next  to  fourth 
vein  gone),  and  in  1  one  posterior  cross- vein  was  gone  while  the  other  was  intact,  but 
thin  in  the  middle. 


34  Linkage  Group  II. 

In  addition  to  modifying  the  wings,  broken  also  affects  the  legs.  The  tibia  on 
the  hind  leg  is  strongly  cur^•ed,  or  arched,  with  the  concave  side  next  to  the  femur, 
and  frequently  the  tarsi  are  shorter  and  swollen. 

Origin. — (M  66.)  Broken  appeared  in  acute  stock.  Only  one  broken  fly  was 
observed,  but  others  may  have  appeared. 

Comparison. — Superficially  broken  resembles  the  sex-linked  character  "crossvein- 
less"  in  D.  virilis  and  D.  melanogaster  (as  noted  above),  and  also  a  non-sex-linked 
character  in  obscura,  the  stock  of  which  has  been  lost  (unpublished  data  of  D.  E. 
Lancefield).     It  is  not  known  how  close  the  resemblance  is  in  the  latter  case. 

LINKAGE  DATA. 
Detection  of  Linkage  in  Group  II. 

Confluent  and  concave. — Four  back-cross  matings  (V  675,  730,  740, 
741)  of  males  heterozygous  for  confluent  and  concave  (in  opposite 
chromosomes)  to  homozygous  concave  females  gave  the  following 
counts:  confluent  213,  concave  213,  confluent  concave  0,  wild-type  0. 
A  similar  back-cross  (V  752)  using  a  male  heterozygous  for  confluent 
and  concave,  but  this  time  in  the  same  chromosome,  gave :  confluent 
0,  concave  0,  confluent  concave  46,  wild-type  44.  These  experiments 
show  that  confluent  and  concave  are  linked. 

Double  with  concave  and  confiuent. — Double  has  proved  to  be  such 
an  unsatisfactory  character  to  work  with,  on  account  of  its  tendency 
to  grade  into  normal,  and  its  eff"ect  on  viability,  that  only  a  few 
tests  were  made  for  linkage  before  the  stock  was  discarded.  These 
are  summarized  below.  Linkage  between  double  and  concave  was 
indicated  by  the  F2  count  from  a  cross  of  concave  by  double.  This 
consisted  of  118  wild-type,  33  concave,  33  double,  without  any  con- 
cave doubles  (P  19,  30,  31).  Similarly,  linkage  between  double 
and  confluent  was  indicated  by  the  progeny  of  matings  (E  998, 
E  1001)  between  confluent  and  double,  using  double  females  and 
males  heterozygous  for  confluent  (dominant)  and  double.  These 
gave:  confluent  142,  double  113,  wild-type  0,  confluent  double  0. 
The  5  wild-type  flies  in  the  latter  case  are  assumed  to  be  genetically 
double. 

Confluent  and  broken. — Linkage  between  these  two  characters 
was  shown  by  the  usual  back-cross  test,  using  heterozygous  males. 
Two  such  matings  (M  291,  M  292)  gave:  23  confluent,  27  broken, 
and  no  wild-type  or  confluent  broken  flies. 

Cross-over  Values  in  Group  II. 

Confluent  and  concave. — Two  back-cross  matings  (experiment  54) , 
using  females  heterozygous  for  the  two  genes  in  opposite  chro- 
mosomes, gave  123  non-cross-over  flies,  and  90  cross-overs.  This 
gives  a  cross-over  value  of  approximately  42  per  cent,  without  any 
correction  for  double  crossing-over. 

Confluent  and  double. — Six  back-crosses  (E  931,  E  947,  E  948, 
E  1032,  E  1033,  E  1034),  using  heterozygous  females  from  confluent 


Linkage  Data.  35 

by  double,  gave:  confluent  343,  double  113,  confluent  double  83, 
wild-type  435.  Counting  only  the  double  flies  (to  avoid  errors  due 
to  viability  and  to  inability  to  exclude  all  double  flies  from  the 
other  two  classes),  this  gives  a  cross-over  value  of  42  per  cent,  which 
is  reliable  at  least  to  the  extent  of  showing  that  confluent  and  double 
are  not  closely  linked.  No  attempt  was  made  to  determine  the 
amount  of  crossing-over  between  double  and  concave,  because  of  the 
difficulty  of  distinguishing  the  two  characters. 

ConUuent  and  broken. — Two  back-crosses  of  heterozygous  females 
(experiment  55)  gave  139  non-cross-over  flies  and  93  cross-overs, 
from  which  we  obtain  a  cross-over  value  of  40  per  cent,  showing 
very  loose  linkage. 

CONSTRUCTION  OF  SECOND-CHROMOSOME  MAP. 

(Figure^?). 

Unfortunately,  broken  appeared  so  recently  that  it  has  only  been 
possible  to  secure  counts  from  the  one  type  of  mating  given  above; 
hence  broken  can  not  yet  be  located  on  the  map. 

Since  the  '^ position"  of  double  is  likewise  uncertain,  only  the 
genes  for  confluent  and  concave  can  be  located.  These  are  probably 
at  least  50  units  apart,  and  perhaps  much  farther,  since  double 
crossing-over  would  probably  prevent  the  detection  of  more  than 
about  42  per  cent  of  crossing-over,  even  if  more  occurred. 


36 


Linkage  Group  III. 


IV.  LINKAGE  GROUP  III. 

This  group  consists  of  the  five  characters  scaly,  spread,  hunch, 
telescoped,  and  garnet.  A  sixth  character,  steel  (for  description 
see  Metz,  1916d),  also  belongs  in  this  group,  but  it  proved  to  be  so 
difficult  to  classify  that  the  stock  was  discarded. 


0     --     sepia  (se) 


6 

7 


24 

24.5 

26 


36 


42 


102 


109 


n 

0      --    Con-fluerrt    (C) 


yellow    (y) 
frayed    (fd) 


crossveinless  (c) 
vermilion        (v) 
vesiculated      (vs) 


oblicjue    (o) 


Sin6ed     (si) 


rugose,  etc.  (r) 


droop    (d) 


42±--     concave   (cc) 


double    (de) 

broken  (b) 

62     - 

-     hairy    (ha) 

67     - 

-     magenta  (m) 

71     - 

-     forked   (f) 

81     - 

-    Triangle  (T) 

86     - 

-     short     (s) 

HE 

0    --     Scaly  (S) 


2i±  --     spread  ?  (sp) 


3I± 


48  ± 


hunch    (h) 


telescoped    (♦) 


9li:--     Garnet  (G) 


Figure  7. 

Crossover  maps  of  linkage  groups  I  to  III  in  Drosophila  virilis.  Maps  II  and  III  are  only  in- 
tended to  give  approximations  of  the  linkage  relations.  Double  and  broken  in  group  II  have 
not  yet  been  located  on  the  map. 


Description  of  Characters. 


37 


DESCRIPTION,  ORIGIN,  AND  COMPARISON  OF  CHARACTERS  IN 

GROUP  III. 

Scaly  (S). 
Description. — Scaly  is  a  dominant,  characterized  by  flattened,  scale-like  omma- 
tidia.  The  eye  usually  has  a  moist  appearance  also.  The  expression  of  this  character 
seems  to  be  influenced  by  environmental  conditions.  In  some  cultures  it  appears  in 
all  flies  heterozygous  for  the  gene;  in  others  many  such  flies  have  eyes  normal  in 
appearance,  although  breeding  tests  show  them  to  carry  the  gene.  It  is  probable 
that  this  irregularity  applies  even  to  homozygous  flies,  although  we  have  not  tested 
this  point  thoroughly.  Scaly  is  not  lethal  when  homozygous  and  pure  stock  is  easily 
maintained. 


IV 

-acute  (ac) 
0- -(-Pinched  (P) 


hur 


V 

0-. 


ip(hp) 


VI 

0--bent{be) 
Net(Nt) 


57  ±-^ 


fused  (fu) 
interrupted(i) 
Branched  (B) 
approximated  (a) 
ruffled  (ru) 

Figure  8. 

Crossover  maps  of  linkage  groups  IV  to  VI  in  Drosophila  virilis. 

The  genes  are  not  placed  on  the  map  in  group  V,  for 

reasons  given  in  the  text  (p.  50). 

Origin. — (V  1128.)  Scaly  was  first  observed  among  the  offspring  of  3  females 
from  one  stock  mated  to  males  from  another  stock.  The  mating  gave  S6  wild-type 
and  23  scaly  individuals,  suggesting  that  one  of  the  parent  flies  was  heterozygous  for 
scaly. 

Spread  (sp). 

Description. — In  spread  flies  the  wings  are  held  out  from  the  body  at  varying 
angles,  usually  between  60°  and  90°.  Otherwise  the  flies  appear  to  be  normal.  Their 
viability  is  poor,  however,  making  the  character  a  difficult  one  to  use  in  linkage 
experiments.  It  can  not  be  classified  accurately  in  combination  with  the  third- 
chromosome  character  hunch,  because  in  the  latter  the  wings  are  often  held  out  at 
an  angle  also. 


38 


Linkage  Group  III. 


Origin. — (P  577.)     One  female  was  found  in  a  bottle  of  droop  stock. 

Comparison. — Spread  resembles  the  third-chromosome  recessive  "spread"  in  D. 
melanogaster  (Dexter,  1914)  and  also  the  second-chromosome  recessive  "spread"  in 
D.  simulans  (Sturtevant,  19216,  p.  186).  It  differs  from  the  former  in  that  the  wings 
are  not  uniformly  held  at  an  angle  of  90°.  In  this  respect  it  agrees  more  closely  with 
"spread"  of  simulans. 

Hunch  (h),     (Figure  9.) 

Description. — Hunch  flies  lack  the  usual  depression  between  the  mesonotum  and 
scutellum  on  the  dorsal  side,  giving  a  hunch-back  appearance.  They  frequently 
show  an  exudation  on  each  side  of  the  thorax  near  the  junction  of  mesonotum  and 
scutellum.  The  wings  are  usually  soft  and  "moist"  in  texture,  and  sometimes  are 
only  partially  expanded  and  are  held  out  at  an  acute  angle  from  the  body. 

Origin. — (L  176.)  Hunch  arose  from  a  mating  of  a  single  female  by  two  males,  all 
from  the  same  mass  culture.  The  offspring  were  35  not-hunch  and  12  hunch.  Evi- 
dently the  female  and  at  least  one  of  the  males  were  heterozygous  for  the  hunch  gene. 

Comparison. — Hunch  agrees  in  its  main  characteristics  with  the  third-chromosome 
recessive  "ascute"  in  D.  melanogaster  and  with  two  similar  characters  in  D.  ohscura, 
one  sex-linked  and  one  non-sex-linked.  The  latter  one  we  have  not  seen,  owing  to 
the  stock  having  been  lost,  but  Dr.  Lancefield  informs  us  that  it  does  not  differ 
noticeably  from  the  other. 


Fig.  9.— Hunch. 


Fig.  10. — Telescoped. 


Telescoped  (t).     (Figure  10.) 

Description. — Telescoped  is  a  recessive,  characterized  bj'  a  greatly  shortened  or 
telescoped  thorax  and  a  consequent  close  approximation  of  the  anterior  and  posterior 
pairs  of  dorso-central  bristles.  Most  telescoped  flies  also  have  small,  narrow  eyes,  or 
in  extreme  cases  no  eyes  at  all,  and  usually  the  hairs  on  the  mesonotum  are  sparse 
and  irregular  in  distribution,  and  the  anterior  dorso-central  bristles  are  small. 

Origin. — (V  974.)  A  female  found  in  confluent  stock  and  segregated  because  she 
had  "groove  eyes"  was  mated  to  normal-eyed  males  from  the  same  bottle.  Among 
the  offspring  was  one  female  \vith  very  narrow  eyes,  which,  when  bred  to  normal- 
eyed  brothers  (or  half  brothers),  gave  225  not-telescoped  and  48  telescoped  progeny. 
At  first  the  telescoped  flies  were  distinguished  merely  by  their  narrow  eyes,  and  it  is 
probable  that  among  the  225  flies  recorded  as  "not-telescoped"  many  telescoped  were 
present.  Indeed,  it  is  probable  that  the  original  female  from  confluent  stock  was 
telescoped  and  one  or  more  of  the  males  to  which  she  was  mated  were  at  least  heter- 
ozygous for  telescoped. 

Comparison. — Dr.  Lancefield  informs  us  that  the  sex-linked  character  "com- 
pressed" in  D.  ohscura  resembled  telescoped,  but  unfortunately  the  stock  of  com- 


METZ 


PLATE  3 


10 


Autosomal  Mutant  Characters  in  Drosophila  virii.is. 
1,  Confluent;    2,  Heterozygoiis  confluent  capsule;    3,  and  5  to  7,  Different  types  of  wings 
from  concave  flies;    4,  Wild-type  (right)  and  concave  (left)  antennir;     8  and  9,  Broken; 
10,  Acute;    11,  Pinched. 


METZ 


PLATE  4 


Autosomal  Mutant  Characters  ix  Drosoimiii.a  \  ikii.is. 

1,  Branched;  2,  Branched  Pinched;  3,  Branched  Pinched  Extra;  4,  Fused  approxi- 
mated; 5,  Ap;)roxiniated;  6,  Interrupted;  7,  Interrupted  approximated;  S,  Heterozy- 
gous interrupted  api)roximated. 


Linkage  Data.  39 

pressed  has  been  lost  and  we  are  unable  to  make  a  detailed  comparison.  The  de- 
scription of  telescoped  suggests  that  of  the  character  "furrowed"  in  D.  melanogaster 
(Morgan  and  Bridges,  1916).  This  is  not  borne  out  by  a  detailed  comparison,  how- 
ever, for  the  modifications  are  not  alike  in  the  two  cases. 

Garnet  (G). 

Description. — Garnet  is  an  eye-color  character  in  which  the  color  is  very  close  to 
Ridgeway's  garnet-brown.  It  is  almost  indistinguishable  from  the  sex-linked  char- 
acter magenta,  but  differs  in  being  a  dominant.  It  is  uniform  and  regular  in  appear- 
ance, and  promises  to  be  a  very  useful  character.  Pure  stock  has  not  yet  been 
obtained,  but  from  one  mating  of  garnet  by  garnet  (M  101)  all  of  the  51  offspring 
were  garnet,  indicating  that  one  parent  was  probably  homozygous.  Tests  are  now 
under  way  to  determine  whether  or  not  garnet  is  lethal  in  the  homozygous  condition. 
Its  viability  is  excellent.  Heterozygous  flies  outcrossed  gave  231  garnet  to  240 
not-garnet  offspring  (M  13,  18,  19,  42,  99). 

Origin. — (M  13.)  The  origin  of  the  garnet  is  not  definitely  known.  It  was  found 
in  a  bottle  of  mixed  stock  carrying  the  sex-linked  characters  vermilion  and  singed, 
and  supposedly  magenta  also.  Tests  revealed  the  presence  of  a  dominant  eye-color 
resembling  magenta,  but  no  actual  magenta.  How  long  this  character  (garnet)  had 
been  present  is  not  known. 

Comparison. — So  far  as  we  are  aware,  this  is  the  only  dominant  mutant  eye-color 
character  of  this  sort  known  in  any  species  of  Drosophila. 

LINKAGE  DATA. 
Detection  of  Linkage  in  Group  III. 

Scaly  and  telescoped. — Scaly  and  telescoped  were  shown  to  belong 
to  the  same  group  by  back-crossing  males  heterozygous  for  the 
respective  genes  (in  opposite  chromosomes)  to  telescoped  females. 
The  following  count  was  obtained  (V  1220,  1244,  1252):  scaly  116, 
telescoped  110,  wild-type  0,  telescoped  scaly  0.  (See  also  under 
scaly,  hunch,  and  telescoped.) 

Steel  and  telescoped. — The  linkage  of  these  two  characters  was 
detected  when  a  heterozygous  male  was  back-crossed  to  a  double 
recessive  female.  This  mating  (V  1191)  gave:  telescoped  12,  steel  13, 
wild-type  1,  telescoped  steel  0.  The  one  wild-type  fly  doubtless 
belongs  in  the  steel  class,  but  failed  to  show  the  spot  in  the  eyes. 
F2  counts  also  indicated  linkage  by  the  absence  of  the  double  recessive 
class. 

Hunch  and  telescoped. — Both  F2  and  back-cross  counts  indicate 
linkage  between  these  characters.  Four  Fi  matings  (L  376,  388,  394, 
400)  gave  the  following  total  of  F2  individuals:  telescoped  67,  hunch 
74,  wild- type  162,  telescoped  hunch  0.  The  back-cross  data  are 
given  in  the  following  paragraph. 

Scaly,  hunch,  and  telescoped. — Two  back-cross  matings  using  heter- 
ozygous males,  with  scaly  in  one  chromosome  and  hunch  telescoped 
in  the  other,  by  homozygous  hunch  telescoped  females  gave  the  fol- 
lowing totals:  hunch  telescoped  132,  scaly  202,  wild-type  58,  hunch  0, 
telescoped  0,  scaly  hunch  0,  scaly  telescoped  0,  scaly  hunch  tel- 


40  Linkage  Group  III. 

escoped  0.  The  58  wild-type  flies  here  should  be  in  the  scaly  class 
but  do  not  show  the  eye  modification.  The  double-recessive  class 
is  small,  as  usual,  on  account  of  low  viability. 

Scaly  and  garnet. — Linkage  between  scaly  and  garnet  was  shown  by 
the  usual  back-cross  test.  This  gave  (M  289,  311)  42  scaly,  49  garnet, 
3  wild-type  (probably  genetically  scaly),  and  no  scaly  garnet. 

Hunch,  telescoped,  and  spread. — The  following  F2  counts  from  a 
mating  of  hunch  telescoped  by  spread  indicate  that  spread  probably 
belongs  in  the  third  linkage  group;  hunch  telescoped  86,  spread  110, 
wild-type  227,  hunch  9,  telescoped  22,  hunch  telescoped  spread  (4?), 
hunch  spread  0,  telescoped  spread  0.  The  four  doubtful  hunch 
telescoped  flies  had  wings  slightly  spread,  but  this  condition  is  occa- 
sionally found  in  hunch  telescoped  flies,  and  the  present  cases  are 
probably  due  to  hunch.  Tests  of  spread  with  members  of  groups  II 
and  IV  show  no  linkage,  and  the  same  is  probably  true  in  the  case 
of  group  V,  although  the  data  are  not  conclusive  as  yet. 

Cross-over  Values  in  Group  III. 

Scaly  and  hunch. — Two  back-crosses  using  heterozygous  females 
gave  35  cross-over  flies  and  99  non-cross-overs  (experiment  57). 
The  wild-type  and  hunch  classes  are  probably  enlarged  at  the  expense 
of  the  other  two  through  the  occasional  failure  of  scaly  to  manifest 
itself,  but  the  error  due  to  this  is  probably  not  as  great  as  that  due  to 
viability.  As  they  stand,  the  data  indicate  approximately  26  per 
cent  crossing-over. 

Scaly  and  telescoped. — Two  back-crosses  (experiment  58),  using 
heterozygous  females  by  telescoped  males,  gave  237  cross-overs  to  313 
non-cross-overs.  These  counts,  like  those  in  the  preceding  case, 
are  subject  to  some  error  due  to  viability  and  possibly  to  errors  in 
classifying  scaly  flies,  but  they  leave  no  doubt  that  the  cross-over 
value  is  high  (43  per  cent  here). 

Scaly  and  spread. — Spread  has  only  been  tested  with  scaly  and 
with  garnet,  and  hence  its  locus  is  not  yet  accurately  placed.  Five 
back-crosses  of  females  heterozygous  for  scaly  and  spread  are  sum- 
marized under  experiment  56.  These  give  a  cross-over  value  of 
approximately  21  per  cent  (counting  only  scaly  flies).  This  is 
subject  to  considerable  error,  but  the  value  is  sm.aller  than  that 
given  by  any  of  the  other  three  characters  when  used  with  scaly  and 
indicates  that  the  locus  of  spread  is  probably  between  scaly  and 
hunch,  or  else  above  scaly. 

Scaly,  hunch,  telescoped. — Under  experiment  60  are  given  the  results 
of  8  back-crosses  of  heterozygous  females  with  hunch  and  telescoped 
in  one  chromosome  and  scaly  in  the  other.  The  cross-over  values 
here  are  approximately  41  units  between  scaly  and  hunch  and  19 
units  between  scaly  and  telescoped.     These  values  are  only  approxi- 


Linkage  Data.  41 

mate,  but  they  are  probably  reliable  to  the  extent  of  indicating  that 
the  serial  order  of  the  genes  is  scaly-hunch-telescoped  and  in  showing 
that  hunch  and  telescoped  are  more  closely  linked  than  are  scaly 
and  hunch.     The  former  value  is  probably  reasonably  accurate. 

Scaly,  hunch,  telescoped,  and  garnet. — The  relative  "location" 
of  garnet  was  determined  by  a  back-cross  involving  garnet  on  one 
side  and  scaly  hunch  telescoped  on  the  other.  This  is  summarized 
in  experiment  61.  It  gives  garnet  a  position  on  the  opposite  end 
of  the  map  from  scaly.  The  numbers  are  not  large  enough  to  give 
accurate  cross-over  data,  but  they  support  the  preceding  experiment 
in  indicating  that  the  loci  of  hunch  and  telescoped  are  relatively 
close  together,  while  that  of  scaly  is  remote  from  both.  That  of 
garnet  is  likewise  remote,  but  in  the  opposite  direction.  As  indicated 
by  the  table,  two  sets  of  values  may  be  considered,  one  based  on  the 
total  count  and  the  other  on  only  the  flies  showing  scaly.  In  either 
case  the  telescoped-garnet  value  is  so  large  as  to  indicate  that  these 
two  loci  are  probably  50  or  more  units  apart.  As  a  result  of  the 
remoteness  of  scaly  and  garnet  from  the  other  two  loci,  double 
crossing-over  is  high.  In  fact  the  single  cross-overs  in  region  2 
are  not  as  numerous  as  either  type  of  doubles  involving  this  region. 
Even  the  triples  appear  to  exceed  this  class  of  singles,  but  this  is 
probably  due  in  part  to  the  failure  of  scaly  to  appear  in  some  of  the 
flies  classified  as  hunch.  Taken  at  their  face  value,  the  data  suggest 
that  hunch  and  telescoped  may  be  in  the  reverse  order  from  that 
given.  This  should  be  kept  in  mind  as  a  possibility,  although  it  is 
opposed  by  the  more  extensive  data  from  experiment  GO,  which  are 
the  ones  used  here  for  the  tentative  determination  of  serial  order. 

Spread  and  garnet. — Two  back-crosses  involving  these  two  genes 
(in  opposite  chromosomes)  gave  59  cross-over  flies  and  82  non-cross- 
overs. This  gives  a  cross-over  value  of  41.8  per  cent  (experiment  59), 
indicating  that  spread  is  remote  from  garnet,  thus  agreeing  with  the 
experiment  involving  scaly  and  spread,  which  placed  spread  near 
the  zero  end  of  the  map. 

CONSTRUCTION  OF  THE  THIRD-CHROMOSOIVIE  MAP. 

(Figure  7.) 

The  data  available  for  constructing  a  map  of  the  third  chromosome 
are  given  in  tables  5  and  6.  For  reasons  given  above,  only  a  rough 
map  can  be  constructed  at  present.  In  table  5  the  data  are  arranged 
according  to  experiments,  w^hile  in  table  6  they  are  arranged  according 
to  the  map  regions  involved.  In  both  tables  two  sets  of  values  are 
given  for  some  of  the  experiments.  The  upper  value  in  these  cases 
is  based  on  all  of  the  flies,  and  the  lower  value  on  only  those  showing 
scaly.  In  the  experiment  involving  scaly  and  hunch  alone  the  two 
values,  thus  obtained,  differ  markedly.     But  the  numbers  are  small 


42  Linkage  Group  III. 

in  this  case,  and  since  these  two  genes  are  involved  in  two  other 
experiments,  giving  larger  counts,  the  latter  are  used  for  calculating 
the  map  distance. 

The  probable  order  of  the  genes  in  group  III  has  been  considered 
above  and  it  remains  to  estimate  the  length  of  the  map  regions. 

With  the  locus  of  scaly  as  the  zero-point,  the  distance  to  spread 
is  estimated  as  about  21  units  on  the  basis  of  experiment  56.  Since 
spread  and  hunch  can  not  be  used  together  satisfactorily,  hunch  is 
located  with  reference  to  scaly  rather  than  spread.  The  value 
believed  to  be  most  reliable  is  that  obtained  from  experiments  60 
and  61,  counting  only  the  scaly  flies.  This  is  approximately  31 
units.  The  hunch-telescoped  value  is  also  taken  from  these  two 
experiments,  giving  an  average  of  approximately  17  units.  Tel- 
escoped is  accordingly  placed  at  48 rb  on  the  map.  The  telescoped- 
garnet  value  of  43  units  is  taken  from  experiment  61.  This  places 
garnet  at  91  on  the  map,  and  it  seems  probable  that  subsequent 
data  will  increase  this  to  well  over  100. 


Linkage  Group  IV. 


43 


V.  LINKAGE  GROUP  IV. 

In  group  IV  only  three  mutant  characters  are  known,  acute, 
pinched,  and  hump.  The  first  is  sometimes  difficult  to  classify,  but 
the  other  two  are  excellent.  Their  linkage  relations  may  be  sum- 
marized by  saying  that  up  to  the  present  time  no  crossing-over  has 
been  detected  between  any  two  of  the  three,  although  fairly  large 
counts  have  been  obtained. 


Table  5. — Summary  of  cross-over  experiments  in  group  III. 


Experiment 
No. 


Mating. 


Cross-over  percentage. 


Total 
flies. 


60 
57 
58 
56 
61 
59 


S  X  h  t 

S  Xh 

S  Xt 

S    X  6p 

S  h  t  X  G.  . 
sp  X  G 


Counting  all:  S-h  40.8,  h-t  18.8 j   1,137 


Counting  only  S:  S-h  31.3. 

Counting  all:  S-h  26.1 

Counting  only  S:  S-h  14.0 

Counting  all:  S-t  43.0 

Counting  only  S:  S-t  39.6 

Counting  all:  S-sp  23.8 

Counting  only  S:  S-sp  21.1 

Counting  axl:  S-h  32.8,  h-t  9.1,  t-G  42.9. 

Counting  only  S:  S-h  30.9 

Counting  all:  sp-G  41.8 


479 
134 

64 
650 
240 
227 
109 
219 

84 
141 


Table  6. — Summary  of  cross-over  data  on  group  III,  arranged  according  to  regions. 


Region. 


Exp.   No. 


Total  flies. 


Cross-overs. 


Per  cent. 


S-sp 
S-h 


h-t 

t-G 
ep-G 


56 
56 
60 
60 
57 
57 
61 
60 
61 
61 
59 


227 
109 

1,137 

479 

134 

64 

219 

1,137 
219 
219 
141 


,  counting 
counting 

,  counting 
counting 
counting 
counting 
counting 


all  flies. .  .  . 
only  S  flies . 
all  flies. .  .  . 
only  S  flies, 
all  flies.  .  .  . 
only  S  flies, 
all  flies.  .  .  . 


54 

23 

465 

150 

35 

9 

72 

214 

20 

94 

59 


23.8 
21.1 
40.8 
31.3 
26.1 
14.0 
32.8 
18.8 
9.1 
42.9 
41.8 


DESCRIPTION  AND  ORIGIN  OF  CHARACTERS  IN  GROUP  IV. 

Acute  (ac).     (Plate  3,  Figure  10.) 

Description. — Acute  is  characterized  by  short,  pointed  wings  and  small  anterior 
dorso-central  bristles.  The  posterior  and  often  the  anterior  sterno-pleural  bristles 
are  reduced  to  hairs,  the  anterior  and  posterior  scutellar  bristles  are  close  together, 
and  one  or  more  of  the  orbital  bristles  are  frequently  absent.  In  addition  the  fifth 
vein,  and  less  often  the  second  vein,  is  slightly  shortened.  The  flies  tend  to  be  small 
and  to  have  short  legs,  but  they  can  not  be  classified  accurately  on  this  basis. 

Origin. — (See  Metz,  1916,  p.  597.)  Acute  arose  in  concave  stock  and  was  at  first 
thought  to  be  a  form  of  concave. 


44  Linkage  Group  IV. 

Pinched  (P).     (Plate  3,  Figure  11.) 

Description. — Pinched  is  a  dominant.  In  heterozygous  flies  the  anterior  cross- 
vein  is  shortened,  so  that  the  third  and  fourth  longitudinal  veins  are  almost  pinched 
together,  and  a  characteristic  short  branch  projects  from  the  fourth  vein  below  the 
first  basal  cell.  Homozygous  flies  exhibit  these  same  features,  and  in  addition  the 
effect  often  extends  to  other  veins;  the  posterior  cross-vein  may  be  shortened  and 
may  lie  diagonally  between  the  fourth  and  fifth  longitudinal  veins  and  the  latter 
may  be  broken  or  shortened.  No  difficulty  is  experienced  in  classifying  pinched 
flies,  but  considerable  variation  is  exhibited  in  both  heterozygous  and  homozygous 
individuals,  and  it  is  not  possible  to  separate  them  in  a  mixed  culture.  The  pinched 
factor  does  not  have  the  completely  lethal  effect  frequently  exhibited  by  dominants 
when  homozygous.  It  does,  however,  have  a  very  detrimental  effect  on  the  viability 
and  fertility. 

Origin. — (L  252.)  Pinched  appeared  in  a  culture  carrying  hump,  and  the  pinched 
factor  shows  complete  linkage  to  that  for  hump.  Evidently  the  mutation  occurred 
in  the  chromosome  carrj'ing  the  hump  factors,  for  the  two  have  remained  inseparable; 
consequently  all  homozygous  pinched  flies  are  hump.  It  should  be  noted  that 
although  pinched  is  always  accompanied  by  hump,  the  converse  is  not  true,  for 
hump  arose  independently  some  months  before  the  appearance  of  pinched  and  the 
original  hump  stock  is  free  from  pinched.  The  two  mutations  may  have  occurred 
in  the  same  locus,  producing  allelomorphic  characters,  but  the  characters  bear  no 
relation  to  each  other,  one  affecting  the  thorax,  the  other  the  wings,  and  probably 
merely  constitute  a  case  of  complete  linkage. 
This  is  made  all  the  more  probable  by  the 
apparent  absence  of  crossing-over  between 
either  of  these  characters  and  acute  (see 
below) . 


Hump  (hp),     (Figure  11.) 

Description. — Hump  is  characterized  by 
an  unusually  arched  and  shortened  thorax 
and  a  dark,  glossj^  body-color  somewhat  like 
that  of  forked.    The  males  may  also  be  dis-  Fig.  ii. — Hump, 

tinguished  by  the  absence  of  color  in  the 
testes,  which  in  normal  flies  are  orange  red.     It  has  excellent  viability  and  fertility. 

Origin. — Hump  was  first  observed  in  a"normal"  stock  descended  from  flies  ob- 
tainedf  rom  Dr.  Roscoe  Hyde,  and  taken  from  astock  originally  secured  in  Terre 
Haute,  Indiana. 

LINKAGE  DATA. 

Detection  of  Linkage  in  Group  IV. 

Acute  and  pinched. — Since  pinched  is  a  dominant  character,  males 
heterozygous  for  acute  and  pinched  were  back-crossed  to  acute 
females.  Two  such  matings  (L  497,  L  505)  gave  the  following  count : 
acute  84,  pinched  100,  wild-type  0,  acute  pinched  0,  which  shows 
that  acute  and  pinched  are  linked. 

Acute  and  hum-p. — In  this  case  the  preUminary  indications  of 
hnkage  were  obtained  from  the  F2  of  a  mating  between  acute  and 
hump.  This  gave  (L  561):  wild- type  68,  acute  27,  hump  16,  without 
any  acute  hump  flies. 


Linkage  Data.  45 

Pinched  and  hump. — The  linkage  of  pinched  and  hump  was  verified 
by  both  F2  counts  and  back-crosses.  In  the  latter,  males  heter- 
ozygous for  pinched  and  hump,  in  the  same  chromosome,  were 
back-crossed  to  hump  females  and  gave  (L  338,  L  344) :  99  wild-type, 
77  pinched  hump,  no  pinched,  and  no  hump  offspring. 

Complete  Linkage  of  Acute,  Pinched,  and  Hump. 

Further  matings  involving  acute,  pinched,  and  hump  have 
indicated  an  extremely  close,  if  not  complete,  linkage  between  them. 
Up  to  the  present  time  no  certain  case  of  crossing-over  has  been 
obtained  among  151  flies  in  back-crosses  involving  pinched  and 
hump  (experiment  62)  and  978  flies  involving  acute  and  pinched 
(experiment  63),  where  heterozygous  females  were  used  and  cross- 
overs would  be  expected  to  appear.  In  one  culture  a  single  fly  with 
abnormal  wing  venation  was  found  which  was  recorded  as  possibly 
pinched,  and  may  have  represented  a  cross-over.  Unfortunately 
it  died  without  giving  any  progeny. 

The  dissimilarity  of  the  three  characters  involved  makes  it  im- 
probable that  they  are  allelomorphs,  as  does  also  the  fact  that  no 
effect  has  been  observed  on  the  heterozygotes  involving  hump  and 
acute,  or  pinched,  hump,  and  acute.  It  should  be  noted  that  these 
flies  were  not  examined  specifically  with  this  point  in  mind,  but  it  is 
unlikely  that  any  appreciable  effect  of  either  gene  would  have  been 
overlooked.  Since  pinched  appeared  in  connection  with  hump, 
and  no  cross-overs  have  been  detected,  the  gene  for  pinched  has 
always  been  accompanied  by  that  for  hump,  and  it  is  not  known 
whether  pinched  would  be  altered  if  the  gene  for  hump  were  elim- 
inated. 

The  complete  linkage  involved  here  suggests  at  once  that  the  genes 
might  be  in  the  small  spherical  m-chromosome  that  resembles  the 
"fourth"  chromosome  of  D.  melanog aster,  in  which  there  appears 
to  be  very  little  crossing-over  (see  p.  76). 


46  Linkage  Group  V. 

VI.  LINKAGE  GROUP  V. 

Group  V  includes  five  characters,  thus  equaling  the  number  of 
the  workable  characters  in  group  III,  the  largest  of  the  other  auto- 
somal groups  (leaving  steel  out  of  account  in  the  latter).  It  also 
presents  the  same  difficulties  as  does  group  III  in  the  way  of  irregular 
characters  and  characters  that  can  not  be  used  satisfactorily  in 
combination. 

DESCRIPTION,  ORIGIN,  AND  COMPARISON  OF  CHARACTERS  IN 

GROUP  V. 
Fused  (fu).     (Plate  4,  Figure  4.) 

Description. — Fused  is  ordinarily  used  as  a  recessive,  but  may  often  be  distin- 
guished in  heterozygous  flies.  In  homozygous  flies  the  third  and  fourth  longitudinal 
veins  are  fused  or  lie  very  close  together  from  the  base  to  the  anterior  cross-vein; 
the  -nings  are  held  at  an  angle  from  the  body;  the  ocelli  and  surrounding  bristles  on 
top  of  the  head  are  entirely  gone;  and  usually  some  or  all  of  the  bristles  on  the 
scutellum  are  lacking.  In  addition,  the  mutant  is  considerably  weaker  than  the 
normal  and  usually  gives  a  deficient  ratio  in  crosses.  In  heterozygous  flies  the  ■s\ings 
appear  to  be  normal,  but  some  or  all  the  bristles  on  top  of  the  head,  and  sometimes 
the  ocelli  also,  may  be  lacking.  The  effect  of  fused  is  exaggerated  by  net.  Flies 
heterozygous  for  fused  and  net,  on  the  average,  lack  more  bristles  on  the  head  than 
those  heterozygous  for  fused  without  net.  The  heads  in  this  case  are  almost  com- 
pletely bald. 

Origin. — (V  778.)  Fused,  like  many  of  the  other  non-sex-linked  characters,  was 
first  observed  in  a  mass  culture. 

Comparison. — Fused  bears  a  slight  resemblance  to  the  sex-linked  "fused"  of  D. 
melanogaster,  but  not  enough  to  indicate  any  probability  of  homology  between  the 
two. 

Interrupted  (i).     (Plate  4,  Figures  6  to  8.) 

Description. — Interrupted  is  a  variable  character  grading  into  normal  and  fre- 
quently not  distinguishable.  In  extreme  cases,  the  posterior  cross-vein  is  broken  or 
almost  gone  (fig.  6,  plate  4).  The  break  may  be  near  the  middle,  but  is  more  often 
near  the  fourth  vein,  or  at  the  junction  with  this  vein.  It  seems  probable  that  inter- 
rupted is  exaggerated  by  approximated,  for  it  seems  to  be  distinguishable  more  often 
in  the  presence  of  approximated  than  in  its  absence.  It  is  difficult  to  make  certain 
of  this  without  extensive  tests,  however,  for  environmental  conditions  appear  to  be 
an  important  factor,  and  these  may  have  been  more  favorable  in  the  former  case. 
Large,  well-fed  flies  tend  to  show  the  interrupted  character  more  often  than  small, 
under-fed  ones.  For  instance,  in  one  count  of  130  flies  (M  1)  from  stock  every  fly 
was  interrupted,  while  in  others,  especially  old  bottles,  many  appear  normal. 

Origin. — (E  15.)  From  a  pair  mating  in  which  both  parents  were  heterozygous 
for  hunch  and  fused,  178  offspring  were  obtained,  of  which  28  lacked  posterior  cross- 
veins.  It  subsequently  developed  that  two  mutant  characters,  interrupted  and  ap- 
proximated, were  involved  here,  and  since  their  distinguishing  features  were  not 
known  at  the  time,  the  records  do  not  tell  the  exact  number  of  each  in  this  culture. 
Since  they  are  both  recessives,  however,  it  is  apparent  that  each  parent  must  have 
been  heterozygous  for  them.  Subsequent  tests  showed  that  the  fused  stock  carried 
approximated  (concealed  by  the  fused  character) ;  hence  the  mutation  responsible  for 
this  character  probably  occurred  eariUer  than  that  for  interrupted. 

Comparison. — Characters  similar  to  interrupted  are  known  in  D.  melanogaster  and 
in  D.  willistoni.  We  have  tested  two  such  characters  in  the  former  species,  but 
neither  resembles  interrupted  sufficiently  to  be  considered  as  a  homologue. 


Description  of  Characters. 


47 


Branched  (B).     (Plate  4,  Figures  1,  2,  and  3.) 

Description. — Branched  is  a  dominant,  irregular  in  its  manifestation  and  incon- 
stant in  its  appearance.  It  is  usually  characterized  by  a  branch  extending  distally 
from  the  posterior  cross-vein.  This  is  often  accompanied  by  slight  protuberances  or 
branches  above  the  second  vein,  near  its  tip,  in  the  region  affected  by  confluent, 
triangle,  and  extra.  The  branch  from  the  posterior  cross-vein  may  be  long  or  short, 
or  may  not  connect  with  the  cross-vein.  When  this  happens  a  short  vein  lies  free 
in  the  cell  beyond  the  posterior  cross-vein.  Sometimes  only  a  vestige  of  this  is 
present,  and  frequently  no  extra  veins  appear.  Homozygous  flies  are  more  extremely 
affected,  on  the  average,  than  heterozygous  ones,  but  the  two  types  over-lap  and 
can  not  be  differentiated.  Homozygous  branched  flies  are  viable  and  fertile  and 
breed  readily  in  pure  stock. 

Origin. — (V  601,  V  606.)  Several  branched  flies  were  found  in  a  stock  bottle. 
From  these,  two  males  were  out-crossed  and  gave  respectively  (V  601)  60  branched, 
79  wild-type,  and  (V  606)  33  branched,  67  wild-type,  showing  the  dominance  of 
branched. 

Approximated  (a).     (Plate  4,  Figures  5,  7,  and  8.) 

Description. — The  nature  of  this  character  may  best  be  appreciated  by  an  ex- 
amination of  figure  5,  plate  4,  and  a  comparison  of  the  wild-type  wing  shown  in 
figure  1  of  plate  2.  The  name  is  derived  from  the  fact  that  the  two  cross-veins  are 
closer  together  than  usual.  This  is  apparently  due  almost  entirely  to  a  modification 
of  the  posterior  cross-vein.  The  junction  of  this  vein  and  the  fifth  is  slightly  nearer 
the  base  of  the  wing  than  usual,  but  is  not  moved  much.  The  junction  with  the 
fourth  vein,  however,  is  shifted  considerably  toward  the  base,  making  the  distance 
between  the  cross-veins  along  the  fourth  vein  about  two-thirds  as  long  as  usual. 
In  wild-type  flies  the  segment  of  the  fourth  vein  between  the  two  cross-veins  is  con- 
siderably longer  than  the  apical  segment  of  the  fifth  vein.  In  approximated  flies  it 
is  shorter.  In  the  latter  the  posterior  cross-vein  is  also  usually  bent  in  an  S  shape 
instead  of  being  straight. 

In  flies  heterozygous  for  approximated  the  condition 
is  somewhat  intermediate  (plate  4,  fig.  8),  but  nearer 
wild-type  than  homozygous  approximated.  Such  flies  are 
readily  distinguished  from  approximated,  but  it  is 
difficult  to  separate  them  from  wild- type.  The  curved 
cross-vein  is  frequently  found  in  heterozygous  flies.  It 
is  not  a  definite  enough  characteristic,  however,  to  per- 
mit the  use  of  approximated  as  a  dominant. 

Origin. — See  under  interrupted  (p.  46). 

Ruffled  (ru).     (Figure  12.) 

Description. — In  ruffled  flies  the  tips  of  the  dorso- 
central  bristles  and  the  hairs  near  them  are  curved 
forward  and  toward  the  midline  of  the  thorax,  as  if 
they  had  been  brushed  back  toward  the  head  and  in 
from  the  sides.  This  gives  the  thorax  a  ruffled  appear- 
ance. The  viability  of  ruffled  flies  is  very  good,  making  the  character  one  of  the  best 
for  linkage  studies. 

Origin.— {M  113.)  24  ruffled  flies  (both  sexes)  appeared  in  the  progeny  of  two 
pairs  from  a  previous  mating  of  two  pairs.  At  least  one  male  and  one  female  of  the 
former  must  have  been  heterozygous  for  the  new  character. 


-^^zf^f^'^ 


Fig.  12.— Ruffled. 


48  Linkage  Group  V. 

LINKAGE  DATA. 

Considerable  difficulty  is  encountered  in  using  the  characters  of 
this  group  in  combination  for  linkage  tests,  because  some  are  irregular 
in  appearance,  and  all  but  ruffled  affect  the  wings.  Branched  is 
unsatisfactory  because  it  does  not  always  manifest  itself;  interrupted 
causes  difficulty  for  the  same  reason,  and  also  because  it  prevents 
the  detection  of  approximated,  in  some  cases,  by  removing  most  of 
the  posterior  cross- vein;  and  finally  fused  often  interferes  with  the 
identification  of  approximated  by  eliminating  the  anterior  cross-vein. 
For  these  reasons  it  is  usually  necessary  to  classify  some  of  the  flies 
as  doubtful,  with  the  result  that  cross-over  values  are  not  accurate. 

The  new  character  "ruffled"  was  obtained  too  recently  to  permit 
of  extensive  use  in  linkage  tests,  but  it  promises  to  be  very  valuable 
for  this  purpose,  since  it  does  not  affect  the  wings. 

Detection  of  Linkage  in  Group  V. 

Branched  and  fused. — The  linkage  of  these  two  characters  was 
revealed  when  heterozygous  males  were  back-crossed  to  fused 
females  (branched  being  a  dominant).  This  type  of  mating  gave 
(E  581,  E  607,  E  615):  140  fused,  199  branched,  and  5  (somatically) 
wild-type  offspring — the  latter  almost  certainly  being  genetically 
branched.     (See   above   under   "branched.") 

Branched  and  approximated. — Linkage  in  this  case  was  likewise 
detected  by  back-crossing  heterozygous  males  (E  1123,  E  1139), 
from  which  the  following  offspring  were  obtained:  branched  115, 
approximated  162,  branched  approximated  0,  and  wild-type  9 
(the  latter  presumably  genetically  branched). 

Fused  and  interrupted. — Linkage  in  this  case  was  indicated  by  the 
F2  results  following  a  cross  of  fused  and  interrupted.  The  counts 
here  were  (E  560,  E  569) :  wild-type  148,  fused  62,  and  interrupted  84, 
with  the  double  recessive  class  lacking. 

Interrupted  and  approximated. — These  characters  were  shown  to 
be  linked  by  the  following  back-cross,  a  heterozygous  male,  which  had 
received  both  mutant  genes  from  one  parent,  mated  to  a  double  reces- 
sive female,  gave  51  interrupted  approximated  flies,  49  wild-type,  two 
approximated  (genetically  interrupted  also),  and  no  interrupted. 

Branched  and  ruffled. — Back-crosses  of  heterozygous  males  were 
used  to  detect  the  linkage  in  this  case  also.  Two  of  these  (M  325 
and  M  327)  gave  67  branched,  38  ruffled,  4  wild-type  (presumably 
genetically  branched),  and  no  branched  raffled. 

Cross-over  Values. 

Fused  and  interrupted. — Data  involving  these  two  characters  are 

subject  to  error,  due  to  the  irregularity  of  interrupted  and  the  low 

viability  of  fused.     The  results  of  6  back-crosses  are  given  under 

experiment  64.    It  is  evident  that  a  large  proportion  of  the  genetically 


Linkage  Data.  49 

interrupted  flies  here  appear  to  be  normal,  hence  it  is  unsafe  to  use 
the  total  count.  Using  only  the  interrupted  flies,  a  cross-over  value 
of  19  per  cent  is  obtained. 

Fused  and  branched. — Back-crosses  of  females  heterozygous  for 
these  two  characters,  in  opposite  chromosomes  gave  49  cross-overs 
in  a  total  of  271  flies,  a  cross-over  value  of  approximately  18  per  cent 
(experiment  65). 

Fused  and  approximated. — Experiment  66  gives  the  results  from 
back-crosses  involving  these  two  characters  alone.  Owing  to  the 
difficulty  of  classifying  approximated  in  the  presence  of  fused, 
only  the  not-fused  flies  are  used  in  calculating  the  cross-over  value. 
These  give  a  value  of  35  per  cent.  Breeding  tests  of  flies  in  both  the 
approximated,  and  the  fused  (not  approximated)  classes,  were  made 
to  verify  the  classification. 

Interrupted  and  branched. — Experiment  67  gives  the  results  of  6 
back-crosses  involving  these  two  characters.  The  data  are  very 
unsatisfactory,  for  both  characters  are  irregular  in  appearance, 
making  the  wild-type  class  very  large,  at  the  expense  of  the  two 
non-cross-over  classes.  Using  only  the  interrupted  flies  a  cross-over 
value  of  2.4  per  cent  is  obtained.  This  seems  to  indicate  close  linkage 
between  the  two,  but  it  needs  to  be  checked  by  the  opposite  type  of 
mating,  using  both  mutant  genes  in  one  chromosome,  to  make  sure 
that  branched  does  not  tend  to  conceal  interrupted. 

Interrupted  and  approximated. — The  regularity  in  appearance  of 
interrupted  varies  considerably  in  different  bottles  (see  description), 
and  for  this  reason  many  of  the  data  can  not  be  used  for  linkage 
calculations.  Furthermore,  it  is  often  difficult  to  classify  approx- 
imated in  the  presence  of  interrupted.  Experiment  68  gives  the 
results  of  6  back-crosses  involving  interrupted  and  approximated 
(both  genes  in  the  same  chromosome).  In  the  first  part  of  this 
experiment,  the  flies  were  all  put  in  the  four  regular  classes,  the 
doubtful  ones  being  classified  as  accurately  as  possible.  Values  have 
been  calculated  here  by  using  (1)  only  the  not-interrupted  flies, 
(2)  only  the  interrupted  flies,  and  (3)  all  flies.  These  are  respectively 
21,  13  and  17  per  cent.  The  second  part  of  the  experiment  is  from 
counts  in  which  especial  attention  was  paid  to  separating  the  inter- 
rupted flies  into  three  classes — those  that  were  approximated, 
those  that  were  not  approximated,  and  those  that  were  doubtful. 
When  only  the  not-interrupted  flies  are  counted,  a  cross-over  value 
of  16  per  cent  is  obtained. 

Another  method  of  handling  the  data  in  the  second  part  of  the 
experiment  has  been  used  to  obtain  the  value  given.  This  permits 
the  use  of  all  flies  by  dividing  the  doubtful  flies  between  the  inter- 
rupted and  the  interrupted  approximated  classes  in  proportion  to  the 
sizes  of  the  latter.     On  this  basis  16.2  per  cent  (35)  are  added  to  the 


50  Linkage  Group  V. 

interrupted  class  and  the  remainder  to  the  interrupted  approximated 
class.  A  calculation  of  the  totals  thus  obtained,  using  all  of  the 
flies,  gives  16.9  per  cent  crossing-over.  Using  only  the  interrupted 
flies  it  gives  17.5  per  cent  crossing-over.  When  all  of  the  data  in 
both  parts  of  the  experiment  are  used,  a  value  of  17  per  cent  is 
obtained.  The  agreement  between  these  various  values  is  sufficient 
to  indicate  that  17  per  cent  is  probably  not  far  from  the  correct 
value. 

Branched  and  ruffled. — RufSed  has  thus  far  only  been  tested  with 
branched.  Four  back-crosses  (experiment  69),  in  which  the  mutant 
genes  were  in  opposite  chromosomes,  gave  200  non-cross-over  flies 
and  198  cross-overs.  This  gives  a  value  of  approximately  50  per 
cent,  showing  that  ruffled  is  remote  from  branched. 

DISCUSSION. 

On  the  basis  of  the  experiments  involving  two  genes  at  a  time, 
the  following   (approximate)   values  are  obtained:  branched-fused 

18  per  cent,  branched-interrupted  2.4  per  cent,  fused-approximated 
35  per  cent,  interrupted-approximated  17  per  cent,  f used-interrupted 

19  per  cent,  branched-ruffled  50  per  cent.  Since  interrupted  is 
placed  here  with  reference  to  both  fused  and  approximated,  it  is 
possible  to  arrange  the  three  genes  in  a  series,  in  which  interrupted 
comes  about  midway  between  the  other  two.  Since  branched  and 
interrupted  appear  to  be  closely  linked,  and  give  nearly  the  same 
cross-over  value  with  fused,  branched  should  fall  near  interrupted. 

It  should  be  possible  to  check  these  values  by  means  of  three-point 
crosses,  but  we  have  not  been  able  to  do  so,  thus  far.  Since  branched 
and  interrupted  are  both  irregular,  it  is  unsafe  to  use  them  in  the 
same  experiment,  and  it  is  unsafe  to  use  fused  with  interrupted 
and  approximated  for  reasons  mentioned  above.  This  leaves  only 
the  combination  branched,  fused,  approximated  with  which  to  make 
the  test.  And  in  the  results  obtained  from  this  (experiment  70) 
the  two  smallest  cross-over  classes  are  so  nearly  equal  that  it  is  impos- 
sible to  determine  which  represents  the  double  cross-overs.  The 
order  should  be  either  fused-branched-approximated,  or  branched- 
f used-approximated,  with  a  value  of  about  19  per  cent  for  the  first 
region  and  38  per  cent  for  the  second,  in  either  case.  If  the  former 
order  is  correct,  the  fused  approximated  value  (60  per  cent)  is  much 
greater  than  that  (35  per  cent)  obtained  when  these  two  characters 
were  used  alone.  On  the  other  hand  this  agrees  better  with  the 
two-point  experiments  involving  interrupted,  because  it  places 
branched  near  interrupted  and  between  the  other  two. 

The  location  of  the  genes  on  a  map  may  be  postponed  until  the 
loci  are  determined  more  accurately.  For  this  reason  the  characters 
are  merely  fisted  in  figure  8  below  a  map  of  57  units  length,  which 
is  the  length  indicated  by  experiment  70. 


Linkage  Group  VI.  51 

VII.    LINKAGE  GROUP  VI. 

After  much  of  the  present  paper  had  been  written,  a  new  mutant 
character  appeared  which  bears  considerable  resemblance  to  the 
fourth-chromosome  character  "bent"  in  D.  melanogaster.  On 
account  of  this  resemblance  it  is  also  called  bent.  It  has  not  been 
studied  fully,  but,  as  indicated  below,  it  does  not  appear  to  be  in 
any  of  the  preceding  linkage  groups. 

Bent  (be).     (Plate  5,  Figure  2.) 

Description. — Bent  appears  to  involve  modifications  in  three  separate  parts  of  the 
fly — legs,  wings,  and  eyes.  None  of  these  is  absolutely  constant,  however.  The 
legs  vary  from  normal  to  a  condition  in  which  they  are  very  much  shortened  and 
more  or  less  distorted.  The  first  part  affected  seems  to  be  the  basal  tarsal  joint  on 
the  hind  legs,  which  is  often  greatly  shortened  and  may  be  thickened,  when  the  legs 
are  otherwise  nearly  normal.  Different  degrees  of  modification  of  the  hind  legs  are 
shown  in  figure  2  of  plate  5.  The  leg  on  the  left  in  this  figure  is  from  a  fly  from 
normal  stock,  those  on  the  right  are  from  bent  stock.  The  effect  on  the  wings  is 
less  marked  and  is  seldom  observed.  Usually  only  one  wing  is  affected.  The  modi- 
fication resembles  the  short  wing  types  in  concave  (plate  3,  fig.  6),  and  frequently 
involves  a  partial  spreading  of  the  wings.  The  sharp  bend  near  the  base  of  the  wing 
characteristic  of  bent  in  melanogaster  is  lacking,  or  at  least  is  much  less  marked. 

The  eye  modification  may  be  described  as  speckled.  Small  dark  specks  appear 
here  and  there  over  the  eye  surface,  due  apparently  to  irregularities  in  the  small 
hairs  between  the  ommatidia.  The  speckling  of  the  eye  is  practically  constant, 
although  very  slight  in  some  individuals. 

It  is  possible  that  the  speckling  of  the  eye  is  a  distinct  mutant  character,  due  to  a 
different  gene  from  that  responsible  for  the  other  two  modifications,  but  this  seems 
highly  improbable.     It  arose  with  bent  and  appears  to  be  inseparable  from  bent. 

Bent  is  greatly  influenced  by  environmental  conditions.  Some  bottles  of  pure 
stock  give  mostly  normal  flies,  with  the  "bent"  ones  appearing  mainlj'^  toward  the 
end  of  the  hatch.  Preliminary  experiments  indicate  that  crowding,  dryness,  or  poor 
food  conditions  favor  the  development  of  the  leg  and  wing  modifications.  When 
mass  cultures  and  pair  matings  were  carried  on  side  by  side,  the  mass  cultures  gave 
a  higher  percentage  of  flies  exhibiting  the  leg  modification.  The  flies  from  the  pair 
matings  were  considerably  larger  and  better  fed  than  those  in  the  mass  cultures. 

Origin. — (M  346.)  From  a  pair  mating  made  to  test  for  a  possible  short  bristle 
character,  the  Pi  female  was  removed  and  put  in  a  fresh  bottle  with  an  Fi  male. 
The  small-bristle  character  failed  to  materialize,  but  in  the  latter  culture  several 
flies  were  found  which  had  short  tarsi  on  the  hind  legs.  These  were  especially  marked 
among  the  last  flies  that  hatched.  Altogether  15  females  and  10  males  vdih.  short 
hind  legs  were  obtained,  together  with  57  females  and  40  males  that  were  not 
noticeably  affected.  The  separation  was  made  on  the  basis  of  the  legs  alone,  as 
the  eye  modification  was  not  noticed  until  afterwards.  The  Pi  female  and  the 
male  used  in  the  second  bottle  had  normal  legs. 

Comparison. — Bent  appears  to  correspond  closely  to  the  bent  of  melanogaster  in 
its  effect  on  the  legs.  The  wing  modification  is  somewhat  similar  to,  but  is  not  so 
nearly  a  duplicate  of,  that  in  melanogaster.  In  both  species  the  character  is  very 
variable  and  dependent  on  environment.  The  same  stock  may  give  at  one  time 
almost  all  normal  appearing  flies  and  at  another  time  almost  all  bent  flies.  We 
have  reared  one  culture  of  bent  melanogaster  in  a  small  v\bX  under  crowded  conditions 
and  found  that  practically  all  exhibited  the  leg  modification,  which  suggests  that 
crowding  may  have  the  same  effect  here  as  in  virilis.      In  these  respects,  then,  the 


52  Linkage  Group  VL 

two  mutant  races  seem  to  agree.     The  eye  modification,  however,  is  absent  or  incon- 
spicuous in  melanogaster  bent. 

Linkage  Tests  with  Bent. 

The  origin  of  bent  indicated  that  it  was  an  autosomal  recessive,  and  this  is  borne 
out  by  subsequent  tests.  Since  bent  was  not  alwa^'s  recognized  at  first,  it  is  impossible 
to  tell  just  how  man}'^  flies  in  the  original  culture  were  bent.  Two  matings  of  normal 
flies  from  this  bottle  both  gave  bent.  Lilcewise  matings  of  bent  flies  gave  bent, 
apparently  pure  stocks.  Several  out-crosses  were  also  made  from  this  bottle  and  no 
bent  flies  were  found  in  Fi  in  any  of  these.  In  F2,  however,  bent  appeared  in  every 
bottle.     All  of  these  results  indicate  that  bent  is  a  recessive. 

Bent  flies  from  the  original  culture  were  out-crossed  to  confluent  garnet  pinched 
flies,  to  branched  flies,  and  to  concave  telescoped  acute  flies.  The  first  four  are 
dominants  representing  groups  II,  III,  IV,  and  V  respectively,  and  the  last  three  are 
recessives  from  groups  II,  III,  and  IV  respectively.  From  the  former  crosses  heter- 
ozygous males  were  back-crossed  to  bent  females,  and  from  the  others  pairs  were 
mated  to  secure  F2  counts.  Unfortunately,  when  this  was  done  it  was  not  known 
that  bent  appeared  best  in  crowded  bottles,  hence  most  of  the  offspring  appeared 
normal  when  the  leg  modification  was  used  for  classifj'ing.  However,  several  cultures 
of  each  type  were  made  up  and  a  sufficient  number  of  unquestionable  bent  flies  have 
appeared  to  give  conclusive  results.  These  experiments  are  being  repeated  and  the 
counts  need  not  be  given  here  in  detail,  but  they  may  be  summarized  by  saying  that 
recombinations  were  obtained  with  all  of  the  above  characters.  Since  these  included 
two  representatives  of  groups  II,  III,  and  IV,  and  one  from  group  V,  the  results  seem 
to  show  conclusively  that  bent  is  in  an  independent  linkage  group  (group  VI)  unless 
some  unusual  genetic  behavior  is  involved,  of  which  there  is  no  evidence. 

Reasons  have  already  been  given  for  considering  linkage  groups  I  to  V  as  repre- 
senting the  five  large  chromosomes.  Bent,  therefore,  appears  to  represent  the  small 
m-chromosome. 

This  fact,  together  with  the  resemblance  of  bent  to  the  bent  of  melanogaster,  which 
is  a  fourth,  or  w-chromosome  character,  provides  evidence  for  considering  the  two 
characters  homologous,  and  for  considering  the  m-chromosomes  of  the  two  species 
homologous.  In  the  case  of  the  large  chromosomes  such  resemblances  as  those  shown 
by  the  two  bents  might  well  be  due  to  accidental  mimicry,  but  in  the  minute  m-chro- 
mosomes the  chance  of  such  mimicry  is  reduced  to  a  minimum. 

Net  (Nt).     (Plate  5,  Figure  1.) 

Description. — Net  is  characterized  primarily  by  its  small,  slender  bristles  and  by 
the  frequent  absence  of  many  of  the  head  bristles.  Associated  with  these  are  a  whole 
series  of  minor  modifications  affecting  nearly  all  parts  of  the  fly.  The  name  is  de- 
rived from  the  network  of  veins  in  extreme  specimens.  Extra  veins  or  bits  of  veins 
appear  frequently  between  the  costa  and  second  vein,  resembling  those  of  triangle 
and  extra;  others  appear  occasionallj''  between  the  second  and  third  veins  near  the 
apex,  and  more  often  in  the  neighborhood  of  the  posterior  cross-veins.  The  latter 
resemble  those  of  the  character  branched.  In  some  specimens  no  extra  veins  are 
present  and  the  wings  appear  to  be  normal,  while  in  others  the  wing  is  a  network  of 
veins.  Between  the  two  extremes  practically  all  intermediates  appear.  Among  the 
other  characteristics  of  net  may  be  mentioned  its  somewhat  smaller  size  and  paler 
color,  the  occasional  speckling  of  the  eyes  like  that  found  in  bent,  but  less  extreme, 
the  absence  or  disarrangement  of  some  of  the  hairs  on  the  thorax  and  head,  the  paler 
bands  on  the  abdomen  and  the  frequent  appearance  of  abnormalities  of  the  abdominal 
segments.  In  some  cases  the  head  is  denuded  of  hairs  and  bristles  over  the  entire 
interocular  region.     Rarely  a  specimen  appears  in  which  the  eyes  and  legs  are  like 


Net.  53 

those  of  bent,  described  above.  It  is  thought  that  these  may  be  homozygous,  but 
the  few  found  thus  far  have  failed  to  breed. 

Net  exhibits  as  many  pecularities  in  behavior  as  it  does  in  appearance.  It  ia 
a  dominant  and  is  lethal,  or  nearly  so,  in  a  homozygous  condition.  No  fertile  homo- 
zygous flies  have  been  obtained.  The  viability  of  net  files  is  very  poor;  their  de- 
velopmental period  is  longer  than  that  of  most  races;  they  begin  hatching  from  two 
to  four  daj's  later  than  their  normal  sibs,  and  they  usually  fall  far  behind  expectation 
in  number. 

Origin. — (L  462.)  Net  was  first  recognized  among  the  offspring  of  a  pair  mating 
in  which  both  parents  were  heterozygous  for  telescoped  and  hump  and  one  parent 
was  heterozygous  for  pinched.  Only  one  fly  was  observed  to  be  net,  but  it  is  possible 
that  other  net  flies  would  have  appeared  if  the  culture  had  been  a  good  one. 

The  peculiarities  of  net  suggest  that  it  is  a  "deficiency"  instead  of 
an  ordinary  gene  mutation,  and  that  it  may  be  analogous  to  Bridges' 
(1921)  "diminished"  in  D.  melanog aster,  with  which  it  agrees  fairly 
closely  in  appearance  and  behavior.  Diminished  is  due  to  the  ab- 
sence of  one  of  the  two  small  7n-chromosomes.  In  our  material 
(of  net),  however,  cytological  examination  has  shown  that  all  of 
the  chromosomes  are  present.  But  crosses  with  bent  support 
the  conclusion  that  net  is  a  deficiency  and  that  it  is  probably  due 
to  the  absence  or  inactivation  of  a  part  of  a  chromosome  containing 
genes  homologous  to  those  in  the  m-chromosomes  ("fourth  chromo- 
some") of  melanagoster. 

When  net  and  bent  are  crossed  the  Fi  net  flies  are  all  bent.  When 
Fi  net  bent  males  are  back-crossed  to  bent  females  the  offspring 
are  of  only  two  classes,  net  bent  and  bent.  This  indicates  that  net 
and  bent  are  in  the  same  Unkage  group  (chromosome)  and  also 
that  net  is  a  deficiency  for  bent.  Corroborative  evidence  is  furnished 
by  the  fact  that  both  net  and  bent  show  independent  segregation 
with  characters  in  the  other  five  linkage  groups.  Fi  net  bent  females 
have  not  been  back-crossed,  because  all  that  have  been  tested 
(about  a  dozen)  have  been  sterile. 


54  Additional  Characters. 

VIII.    ADDITIONAL  CHARACTERS. 

In  addition  to  the  above  characters  whose  linkage  relations  are 
known  to  some  extent,  the  following  characters  have  been  found, 
but  have  not  yet  been  placed  with  certainty  in  any  linkage  group. 
These  are  characters  that  are  difficult  to  test  for  linkage,  because  of 
poor  viability,  irregularity  of  appearance,  or  interference  with  the 
classification  of  other  characters.  Since  the  linkage  tests  have  not 
been  completed,  none  of  the  data  are  included  here. 

Extra  (E).     (Plate  5,  Figure  3.) 

Description. — Extra  is  a  dominant  character  somewhat  like  the  sex-linked  domi- 
nant triangle.  It  is  not  uniform  in  appearance,  but  usually  takes  the  form  of  a  V- 
shaped  branch  above  the  second  vein  near  its  apex.  Occasionally  it  is  lacking  and 
the  fly  appears  normal.  In  combination  "svith  the  other  wing  characters,  concave, 
confluent,  pinched,  or  branched,  extreme  effects  are  produced.  In  the  first  case  the 
wing  is  apt  to  be  crinkled  and  the  costal  vein  thick  around  the  end  of  the  wing.  In 
the  others  more  extra  veins  appear  than  would  come  from  the  sum  of  the  two  char- 
acters acting  alone.  With  confluent  the  effect  of  both  characters  is  exaggerated;  an 
irregular  network  of  veins  is  apt  to  be  present,  and  thickenings  appear  at  the  junction 
of  cross-veins  and  longitudinal  veins.  With  pinched,  extra  veins  appear  not  only 
above  the  second  vein,  but  also  between  the  third  and  fourth  (the  region  affected  by 
pinched).  With  branched  a  cluster  of  veins  usually  appears  in  both  the  region 
normally  affected  by  extra  and  in  that  normally  affected  by  branched.  When  all 
three  characters — pinched,  branched  and  extra — are  combined,  the  three  correspond- 
ing clusters  of  veins  appear  (plate  4,  fig.  3). 

Origin. — (M  21.)  Among  the  offspring  of  a  spine  female  by  confluent  (dominant) 
concave  males  one  confluent  female  appeared  with  net-like  wings.  When  mated  to 
normal-appearing  brothers  this  female  produced  the  following  classes  of  offspring: 
confluent  16,  extreme  confluent  (net-like)  39,  wild-type  39,  and  extra  vein  19.  This 
and  subsequent  matings  indicate  that  the  net-lilce  condition  in  the  confluent  flies  and 
the  extra-vein  condition  in  part  of  the  others  is  due  to  the  same  gene — that  for 
"e.xtra." 

Spine  (sn).     (Plate  5,  Figure  4.) 

Description. — The  only  distinguishing  characteristic  that  we  have  been  able  to 
detect  in  spine  is  the  presence  of  a  small  bristle  arising  from  one  of  the  sense-organs 
on  the  third  vein  opposite  the  posterior  cross-vein.  It  is  very  inconstant  in  appear- 
ance, frequently  being  absent  or  present  in  only  one  wing.  It  ordinarily  behaves  as 
a  recessive,  but  in  at  least  one  case  it  was  manifest  in  an  Fi  fly  from  an  out-cross, 
which  suggests  that  it  may  occasionally  act  as  a  dominant. 

Origin. — (E  1286.)     One  male  from  pinched  stock,  found  by  Mr.  M.  Demerec. 

Capsule  (op). 

Description. — Capsule  is  a  recessive  character  affecting  the  wings.  As  the  name 
implies,  the  wing  is  swollen  and  cylindrical  like  a  capsule.  AU  trace  of  venation  is 
gone.  Both  wings  are  bladder-like  and  stand  out  at  right  angles  from  the  thorax. 
The  viability  and  fertility  of  capsule  flies  are  very  poor  and  the  stock  was  lost  before 
linkage  tests  were  made.  The  males  appeared  to  be  sterile,  although  only  a  few 
were  tested.  In  the  heterozygous  condition  capsule  has  an  exaggerating  effect  on 
confluent,  as  shown  in  figure  2  of  plate  3.  All  of  the  confluent  flies  from  a  cross  of 
confluent  by  a  capsule  were  of  this  extreme  tj^pe. 


METZ 


PLATE  5 


CM 


X 


>  '^i 


—      r. 


C    ^3 

■T.     ~ 


5       ^ 


v. 


Minus.  55 

Origin. — (L  92.)  Two  capsule  flies,  one  male  and  one  female,  were  found  among 
the  ofTspring  of  a  concave  female  from  stock.  The  capsule  female  mated  to  normal 
brothers  gave  24  capsule  to  60  not-capsule  offspring.  Three  capsule  females  from 
this  culture  mated  to  confluent  males  gave  9  wild-type  and  13  exaggerated  confluent 
flies  of  the  type  described  above;  3  other  capsule  females  mated  to  wild-type  males 
from  stock  gave  only  wild-type  offspring  (about  20). 

Minus  (mi). 

Description. — Minus  flies  frequently  lack  one  or  more  of  the  thoracic  bristles, 
particularly  the  scutellar  or  dorso-central  bristles.  Occasionally  the  effect  may  be 
reversed,  and  one  or  more  bristles  may  be  doubled.  The  character  is  very  inconstant 
in  appearance  and  seems  to  be  affected  greatly  by  environmental  conditions.  In 
some  cases  nearly  all  the  flies  in  the  homozj'^gous  stock  will  appear  normal.  The 
character  is  a  recessive. 

Origin. — (L  22.)     Many  flies  from  a  stock  carrying  wax. 


56  Comparison  of  Characters 

IX.     COMPARISON  OF  MUTANT  CHARACTERS  IN 
D.  VIRILIS  WITH  THOSE  IN  OTHER 
SPECIES  OF  DROSOPHILA. 

Several  species  of  Drosophila  have  now  been  studied  sufficiently 
to  permit  a  comparison  of  their  genetic  behavior.  With  the  excep- 
tion of  D.  virilis  and  of  the  well-known  D.  melanogaster,  these  are 
listed  in  table  7,  together  with  references  to  the  papers  dealing  with 
them  and  a  statement  as  to  the  number  of  mutant  characters  in  each. 
Their  chromosomal  relations  may  be  determined  by  reference  to 
figures  1  and  2.  By  examining  the  table  an  estimate  may  be  made 
of  the  extent  of  the  published  information  on  the  various  species. 


Table 

7. 

Species. 

References. 

Mutant  characters.          Chromosomes. 

Characters 
mentioned 

not 
described. 

Sex-linked. 

Autosomal. 

Hap- 

loid 
No. 

Type. 

Reces- 
sive. 

Domi- 
nant. 

Rcccs-  Domi- 
sive.      nant. 

D.  affinis  Sturt 

D.  busckii  Coq 

D.  caribbea  Sturt  . . 
D.  funebris  Fabr. .  . 

D.  hydei  Sturt 

D.  immigrans  Sturt . 
D.  obscura  Fall .... 

D.  repleta  Will 

D.  similis  Will 

D.  simulans  Sturt .  . 

D.  willistoni  Sturt. . 

Hyde,  R.  R.,  1915 

1 
2 
1 

5 

4 
4 
6 

K 
A 
L 
G 

2 
S 

2 

Non-dis- 
junction. 

Warren,  D   C  ,  1917.      . 

Sturtevant,  192  If 

Sturtevant,  A.  H.,  1918    . 

1 

Mohr  and  Sturtevant,  1919 
Sturtevant.  A.  H.,  1921a.. 
Sturtevant,  A.  H.,  1921c.. 

1 

1 





Hyde,  R.  R.,  1915 

1 
1 
1 

6 

I 

Hyde,  R.  R.,  1922 

Metz  and  Metz,  1915 

4 

D 

Sturtevant,  1921c 

Metz,  1916d 

1 
28 

2 

5 

J 

Lancefield,  D.  E.,  1922... 
Sturtevant.  A   H  .  1921c 

1 

Sturtevant,  A.  H..  1915.  . 
Sturtevant,  A.  H.,  1921c 

1 

6 

I 

Metz,  1916</ 

1 

6 

4 

F 
A 

Sturtevant,  A.  H.,  1921a. 
Sturtevant,  A.  H.,  19216. 
Sturtevant,  A.  H.,  1921rf 

7 

11 

1 

1 

1 

Lancefield  and  Metz,  1921 
Lancefield  and  Metz,  1922 



3 

See 
fig.  2 

28 

1 

In  the  following  comparisons,  unpublished  as  well  as  published 
information  has  been  drawn  upon  freely,  with  the  consent  of  the 
investigators,  as  mentioned  on  page  13  under  "Acknowledgments." 

At  the  outset  of  a  comparison  of  this  kind,  which  seeks  to  detect 
homologies,  it  is  necessary  to  inquire  as  to  what  evidence  is  to  be 
considered  reliable  in  the  absence  of  direct  hybridization  tests. 
As  stated  in  the  introduction,  the  failure  of  the  above  species  to 
hybridize  (with  one  exception  noted)  presents  a  serious  obstacle  to 
this  particular  feature  of  the  work. 


In  Different  Species.  57 

Direct  proof  of  homology  of  individual  mutant  characters  can 
hardly  be  obtained,  except  by  hybridization.  On  the  other  hand, 
it  ought  to  be  possible  to  obtain  evidence  very  nearly  as  conclusive 
by  the  use  of  series  of  characters,  even  without  hybridization  tests, 
especially  when  several  related  species  are  being  studied.  For- 
tunately, in  the  case  of  the  drosophilas,  deductions  from  such  evidence 
receive  added  support  from  analogy  with  the  one  case  in  which  hybri- 
dization is  possible.  For  example,  we  may  consider  the  case  discussed 
below,  involving  the  four  sex-hnked  characters  yellow,  crossveinless, 
singed,  and  forked  in  virilis  and  those  of  the  same  names  in  melano- 
gaster.  These  characters  are  morphologically  similar  in  the  two 
species,  and  in  addition  they  are  all  sex-linked  and  their  genes  come 
in  the  same  order  and  at  approximately  proportional  distances  on 
the  chromosome  maps.  This  agreement  in  several  respects  affords 
ground  for  considering  them  homologous,  but  the  probability  is 
increased  still  more  by  analogy  with  the  known  cases  of  homology 
in  D.  simulans  and  melanog aster.  Yellow  and  forked  and  three 
characters  whose  genes  occupy  intermediate  loci  in  D.  simulans 
have  been  shown  by  Sturtevant  (1921a)  to  be  homologous  to  cor- 
responding characters  in  melanogaster.  The  map  relations  of  these 
are  shown  in  figure  13.  To  be  sure,  the  two  species,  melanogaster 
and  simulans,  are  so  nearly  identical  that  resemblances  in  genetic 
behavior  would  be  expected  to  be  closer  here  than  in  the  other  cases, 
but  the  analogy  between  the  proven  relations  here  and  the  apparent 
relations  in  the  other  cases  can  not  but  add  probability  to  the  latter. 

This,  however,  does  not  obviate  the  necessity  for  extreme  caution 
in  considering  possible  homologies.  The  dangers  in  this  regard 
have  often  been  pointed  out.  It  is  well  known,  for  instance,  that 
mimic  characters  may  appear  in  one  species,  which  are  somatically 
identical,  or  nearly  so,  but  which  are  due  to  mutations  in  different 
loci  or  even  in  different  chromosomes.  Likewise  there  is  the  possi- 
bility that  identical  mutations  may  give  different  results  in  different 
species.  These  and  other  possibilities  of  error  emphasize  the  need 
of  a  relatively  large  amount  of  data  before  cases  of  homology  can 
be  considered  as  established.  In  the  present  paper,  therefore,  we 
will  confine  ourselves  to  a  consideration  of  the  trend  of  the  evidence, 
recognizing  the  fact  that  subsequent  data  may  modify  the  case. 

COMPARISON  OF  SEX-LINKED  CHARACTERS. 

The  "Forked  and  Singed"  Series. 

The  most  extensive  series  of  similar  mutant  characters  in  the 
drosophilas  includes  those  called  "forked,"  "singed,"  or  "stubby." 
The  most  prominent  characteristic  common  to  these  is  the  modified 
thoracic  bristles.  One  or  more  mutants  in  this  category  are  known  in 
each  of  the  following  species:  D.  melanogaster,  D.  lirilis,  D.  willistoni, 


58 


Comparison  of  Characters 


D.  melanogaster     D.  simulans 


yellow    -. 
prune     -■ 


rubv 


0.0- 
I.  I- 


7.  5> 


-0.0      .. 
-3.0      ■- 


yellow 
prune 


11.3      --     rubyoid 


g 


arnet     --  44.4 


44.8     --    carmine 


D.  obscura,  D.  simulans,  and  D.  funehris.  In  all  of  these  the  charac- 
ters are  sex-linked  and  with  one  exception^  there  are  no  autosomal 
characters  of  this  kind  known.  The  maximum  number  of  loci 
involved  is  two,  and  two  are  repre- 
sented in  all  but  the  last  two 
species.  In  D.  melanogaster  at  least 
five  allelomorphs  are  known  in  the 
forked  locus,  and  two  in  the  singed 
locus  (Mohr,  1922,  and  unpublished 
data  of  C.  B.  Bridges).  In  each 
case  these  express  different  degrees 
of  modification  in  the  same  direc- 
tion. Similarly  in  D.  willistoni  two 
''forked"  allelomorphs  are  known, 
one  being  more  extreme  than  the 
other. 

The  resemblance  between  these 
characters  in  the  different  species  is 
so  obvious  as  to  suggest  at  once  that 
some  homology  exists  between 
them.  Indeed,  homology  has  been 
demonstrated  in  the  case  of  forked 
melanogaster  and  forked  simulans, 
as  noted  above.  But  in  the  species 
in  which  two  non-alielomorphic 
characters  are  concerned  it  is  neces- 
sary to  find  some  distinction  be- 
tween the  two  before  a  comparison 
can  safely  be  made.  Mohr  (1922)  fig.  is.— x-chromosome  maps  of  d.  TTietono- 
has  given  a  detailed  account  of 
forked  and  singed  in  D.  melano- 
gaster, and  has  indicated  a  series  of  differences  between  them.  In 
order  to  determine  whether  or  not  any  of  these  differences  will  hold 
constantly  between  the  non-allelomorphic  mutants  of  this  type  in 
the  other  species,  we  have  examined  specimens  of  all  of  the  available 
mutants.  These  are  included  in  the  list  on  page  59,  together  with 
those  (in  parenthesis)  which  we  have  not  been  able  to  examine  (due 
mainly  to  loss  of  the  stocks). 

Before  considering  the  relationships  of  these  we  may  give  brief 
comparative  descriptions  of  the  different  characters.  These  include 
practically  all  of  the  features  in  which  differences  have  been  found. 
Except  where  specified  to  the  contrary  the  descriptions  are  based  on 
comparisons  of  male  specimens  side  by  side  under  the  microscope. 

'  A  recessive,  semi-lethal  character  in  D.  simulans  (unpublished  data  of  Dr.  A.  H.  Sturtevant) 
with  stubby  bristles,  not  unlike  those  of  the  less  extreme  stubby  or  forked  mutants. 


forked     -■    56.3 


57.  2      -■      forked 


gastcr  and  D.  simulans  (from  Sturtevant 
1921a). 


In  Different  Species.  59 

In  most  cases  there  is  a  moderate  range  of  variability  in  the  character, 
so  the  description  is  made  to  represent  the  average  condition  as 
nearly  as  possible. 

D.  melanogaster:  forked,  (forked-2),  forked-3,  (forked-4),  forked-5. 

singed,  singed-2. 
D.  wiUisloni:       forked-l,  (forked-2). 

stubby. 
D.  virilis:  forked. 

singed. 
D.  obscura:  singed. 

(stubby) . 
D.  simulans:        forked. 
D.  funebris:         forked. 

Drosophila  melanogasteh. 

Forked. — Effect  moderate  to  extreme.  Bristles  shortened,  t^visted,  sharply  forked; 
not  depressed.  Hairs  somewhat  stubby,  not  depressed  or  curled.  Both  sexes  fertile. 
Eggs  normal.     Heterozygous  females  apparently  normal. 

Forked-2. — (From  Mohr,  1922.)  Effect  slight,  variable,  more  pronounced  in 
females  than  in  males.  Bristles  long,  not  crinkled  or  t'v^asted;  one  or  more  usually 
forked  at  tip.  Head  bristles  rarely  affected.  Presumably  hairs  and  bristles  not 
depressed;  females  fertile;  eggs  normal.  (These  features  not  mentioned  in  descrip- 
tion.) 

Forked-3. — Effect  slight.  Bristles  mostly  not  forked,  but  only  stubby;  not  de- 
pressed; few  bristles  forked  at  tip,  or  bent  sharplj^  back,  hook-shaped;  bristles  not 
wavy.  Hairs  on  thorax,  abdomen,  legs,  and  wings  normal  or  nearly  so;  bristles 
bordering  segments  of  abdomen  curled  slightly.  Hairs  on  arista  apparently  normal. 
Both  sex3s  fertile;  eggs  normal.     Heterozygous  females  not  examined. 

Forked-4.— (From  Mohr,  1922.)  Effect  strikingly  like  that  of  singed.  Differs 
only  slightly.  Bristles  and  hairs  all  over  the  body  affected;  bristles  curled  as  in 
singed.  "The  bristles  are  slightly  thicker  in  forked-4  than  in  singed  flies,  small 
bifurcations  of  the  bristles  are  somewhat  more  frequent  in  the  former,  and  the  altera- 
tion of  the  small  hairs  all  over  the  body  seems  to  be  slightly  less  pronounced  in 
forked-4  than  in  singed  individuals."  Females  fertile,  eggs  presumably  normal. 
Heterozygous  females  not  examined. 

Forked-5. — Effect  extreme.  Bristles  heavy,  depressed,  greatly  twisted,  knotted 
and  forked,  projections  sharp,  hairs  on  head,  thorax,  abdomen  and  legs  depressed 
and  often  curled;  hairs  on  costa  hea\'>',  stand  out  at  a  greater  angle  than  usual. 
Hairs  on  arista  practically  normal.  (See  also  under  singed.)  Both  sexes  fertile; 
eggs  normal.  Heterozygous  females  not  examined.  It  is  possible  that  forked-5 
and  forked-4  are  identical. 

Singed. — Effect  extreme,  but  not  as  extreme  as  forked-5.  Very  much  like  forked-5 
in  most  respects.  Bristles  longer  and  more  slender,  but  twisted  and  forked  in  much 
the  same  manner.  Hairs  on  entire  fly  essentially  the  same  as  in  forked-5.  Females 
sterile.  Eggs  abnormal,  short  filaments  (Mohr,  1922).  Double  recessive  singed-forked 
indistinguishable  from  singed  (Mohr,  1922).  Double  recessive  singed-forked-4  in- 
distinguishable from  singed  or  from  forked-4  (Mohr,  1922).  Heterozygous  females 
not  examined. 

Singed-2. — Effect  slight  to  moderate,  much  less  extreme  than  singed.  Bristles 
wavy,  somewhat  depressed,  a  few  slightly  forked  at  the  tip.  Hairs  on  thorax  de- 
pressed, those  on  abdomen,  legs  and  wings  practically  normal.  Arista  practically 
normal.  Females  fertile;  eggs  normal.  (This  is  not  singed-2  of  Mohr,  1922,  which 
was  indistinguishable  from  singed.)     Heterozj'gous  females  not  examined. 


60  Comparison  of  Characters 

Drosophila  virilis. 

Forked. — Effect  moderate.  Bristles  erect,  heavier  and  shorter  than  normal,  wavy, 
a  few  forked  sharply  at  tip.  Hairs  on  entire  fly  somewhat  shortened  but  not  de- 
pressed or  curled;  those  on  arista  very  short,  those  on  costa  stand  out  at  an  angle  of 
about  60°.  Body-color  darker  and  glossier  than  normal.  Both  sexes  fertile;  eggs 
normal.     Heterozygous  females  have  short  bristles. 

Singed. — Effect  extreme;  probably  most  extreme  of  all  the  characters  in  the  present 
series.  Bristles  and  hairs  much  like  those  of  singed  and  forked-5  melanogaster,  but 
more  extremely  affected.  Bristles,  especially  on  scutellum,  greatly  depressed,  short, 
thick,  twisted,  curled  or  knotted,  and  forked.  Hairs  on  body  and  legs  depressed, 
curled,  and  shortened;  those  on  costa  affected  as  much  as  in  forked;  those  on  arista 
nearly  normal,  not  as  short  as  in  forked.  Double  recessive  singed-forked  is  like 
singed,  but  has  glossy  body  like  forked.  Heterozygous  females  have  short  bristles. 
Females  fertile;  eggs  normal. 

Drosophila  willistoni. 

Stubby. — Effect  slight  to  moderate.  Bristles  heavy,  sharply  forked,  not  depressed. 
Hairs  on  thorax,  abdomen,  head,  legs,  and  wings  apparently  normal;  those  on  arista 
apparently  normal,  not  branched.  Females  fertile;  eggs  normal.  Heterozygous 
females  not  examined. 

Forked. — (From  two  alcoholic  specimens.)  Effect  moderate.  Bristles  depressed, 
curled,  few  forked.  Hairs  on  thorax  decidedly  depressed,  somewhat  curled;  those  on 
abdomen  apparently  same,  those  on  legs  and  wings  apparently  slightly  affected. 
Hairs  on  arista  long,  slender,  normal  or  nearly  so,  not  branched.  Females  sterile; 
eggs  dissected  from  alcoholic  specimen  have  verj'  short,  broad  filaments,  decidedly 
abnormal,  like  those  of  singed  melanogaster .     Heterozygous  females  not  examined. 

Forked-2.—{Y\om.  Lancefield  and  Metz,  1922,  p.  217.)  Effect  extreme.  Bristles 
twisted,  thickened,  forked,  depressed.  Hairs  short,  depressed,  somewhat  curled. 
Hairs  on  arista  branched.  Females  sterile;  eggs  not  examined  (stock  lost).  Heter- 
ozygous females  not  examined. 

Drosophila  obscura. 

Stubby.— {Yrom  description,  D.  E.  Lancefield,  1922,  p.  372.)  "Their  main  charac- 
teristic is  the  shortening  of  the  macrochaetse  and  a  bending  or  twisting  of  the  bristles 
that  occurs  rather  infrequently.  It  does  not  resemble  the  forked  mutants  of  other 
species." 

Singed. — Effect  slight  to  moderate.  Bristles  wavy,  some  slightly  forked  at  tip, 
somewhat  depressed.  Hairs  on  thorax  depressed;  those  on  abdomen  and  legs  not 
depressed.  Hairs  on  arista  slightly  shortened,  not  branched.  Body  glossy  black; 
females  sterile;  no  eggs  have  been  found,  although  females  have  been  dissected  and 
attempts  have  been  made  to  get  them  to  lay  eggs.  It  is  possible  that  eggs  do  not 
mature  in  singed  females.  Bristles  of  heterozygous  females  often  shorter  than  normal 
(possibly  not  constant). 

Drosophila  simulans. 

Forked. — Effect  moderate  to  extreme;  intermediate  between  forked  and  forked-5 
(in  D.  melanogaster)  to  which  it  is  allelomorphic.  Some  hairs  on  arista  branched,  not 
short  and  stubby.  Females  fertile,  eggs  normal.  Resembles  most  closely  forked 
melanogaster.    Heterozygous  females  apparently  normal. 

Drosophila  funebris. 

Forked. — Effect  slight  to  moderate.  Bristles  stubby,  stout,  not  wavy;  a  few  forked 
sharply  near  tip,  not  depressed.  Hairs  on  thorax,  abdomen,  legs,  and  wings  shortened, 
but  not  depressed  and  curled  as  in  singed  virilis.    Some  of  the  bristles  on  abdomen 


In  Different  Species.  61 

forked.     Hairs  on  costa  stand  out  at  an  angle  of  about  60°.     Females  fertile;  eggs 
normal.    Resembles  most  closely  forked  virilis.      Heterozygous  females  not  examined. 

Relationships. 

One  of  the  first  points  revealed  by  this  comparison  is  that  a 
similarity  in  name  does  not  necessarily  indicate  a  close  similarity  in 
the  appearance  of  the  characters  in  different  species.  For  instance, 
forked-1  and  forked-2  in  willistoni  suggest  singed  in  mrilis  instead 
of  forked,  which  is  more  like  stubby  in  willistoni. 

Our  search  for  some  feature  upon  which  to  base  a  dichotomous 
separation  of  the  characters  in  the  whole  series  has  been  largely 
unsuccessful.  The  range  of  modifications  shown  by  the  forked 
allelomorphs  in  melanogaster,  for  instance,  covers  most  of  the  condi- 
tions found  in  any  of  the  ''forked,"  "singed,"  or  ''stubby"  characters 
in  the  other  species.  No  single  criterion,  therefore,  can  be  used 
exclusively  for  determining  homology  or  lack  of  homology.  The 
best  we  can  do  at  present  is  to  relate  the  characters  on  the  basis  of 
the  degree  of  resemblance. 

The  two  singed  allelomorphs  in  melanogaster,  the  two  forked 
allelomorphs  in  willistoni,  and  singed  in  obscura  agree  in  regard  to 
female  sterility  and  presumably  in  regard  to  egg  abnormality  (see 
descriptions).  This  gives  good  ground  for  considering  them  to  be 
parallels.  It  is  supported  also  by  the  general  appearance  of  the 
characters,  which  are  of  the  t}n?^  having  twisted  or  curled  rather 
than  jagged  and  sharply  bent  bristles.  Correlated  with  this  are  the 
depressed  bristles  and  curled  and  depressed  hairs  on  the  thorax. 
We  may  group  these  characters  together,  then,  in  the  "singed" 
series. 

The  other  character  in  willistoni  (stubby)  differs  in  all  of  these 
respects  and  bears  a  closer  resemblance  to  the  forked  allelomorphs 
of  melanogaster.  So  we  may  group  these  together  in  the  "forked" 
series.  In  obscura  the  character  stubby  represents  such  a  slight 
modification  that  it  is  hard  to  compare  with  the  others,  especially 
since  no  specimens  are  available  for  examination.  Since  singed 
seems  to  belong  to  the  singed  series,  however,  stubby  may  tentatively 
be  correlated  with  the  forked  series. 

These  relations  are  shown  schematically  in  figure  14,  in  which  the 
chromosome  maps  are  oriented  so  that  the  loci  of  parallels^  cor- 
respond. 

In  simulans  forked  has  been  shown  by  Sturtevant  (1.  c.)  to  be 
allelomorphic  to  that  in  melanogaster,  and  consequently  the  simulans 
map  would  correspond  to  that  of  melanogaster,  and  iwojy  be  omitted 
here. 

*  The  term  parallel  is  used  to  indicate  a  resemblance  which  suggests  homology. 


62 


Comparison  of  Characters 


It  remains,  then,  to  determine  whether  or  not  forked  and  singed 
in  virilis  and  forked  in  funebris  will  fit  into  the  above  series.  The 
resemblance  between  the  forked  characters  in  the  latter  two  species 
has  been  noted  under  the  description  of  forked  (see  also  Sturtevant, 
I.e.)-  The  resemblance  is  very  close  in  nearly  all  respects,  hence  these 
two  may  tentatively  be  classed  as  parallels. 

D.obscura 


D.  melanogabter 


D.  wiMi5toni 


singed 


-  forked 


-  stubby 


■  forked 


-smged 


■  stubby 


Figure  14. 
X-chroraosome  maps  of  three  species  of  Drosophila,  indicating  loci  of  forked,  singed,  and  stubby. 

We  need  to  consider,  therefore,  only  the  singed  and  forked  in 
virilis  in  relation  to  the  others.  In  doing  this  it  is  evident  at  the 
outset  that  the  most  important  criteria — sterility  and  egg  modifica- 
tions— can  not  be  used.  Fortunately,  however,  the  two  characters 
are  well  marked  (i.  e.,  fairly  extreme)  and  are  different  in  several 
respects.  In  singed  the  bristles  are  twisted  and  depressed,  so  that 
they  lie  almost  flat,  especially  on  the  thorax.  The  hairs  are  curled 
and  are  also  depressed.  In  forked  the  bristles  and  hairs  are  little 
if  any  depressed,  and  are  not  noticeably  curled.  The  bristles  likewise 
tend  to  be  of  the  sharply  forked  rather  than  the  curled  type. 

None  of  these  features  is  diagnostic,  but  they  all  tend  to  put 
singed  with  the  singed  series.  If  a  singed  allelomorph  with  sterile 
females  were  present  in  virilis  the  case  would  be  much  stronger,  but 
until  some  supporting  or  contradicting  evidence  is  obtained  the 
above  relationships  may  be  considered  as  at  least  probable. 

This  view  receives  considerable  support  from  the  relations  of  other 
characters  and  the  sequence  of  the  loci  on  the  map,  as  discussed 
below. 


In  Different  Species.  63 

Comparison  with  Sex-Linked  Characters  in  Drosoimiila  melanogaster. 

The  parallelism  between  yellow  and  forked  in  D.  mrilis  and 
D.  melanogaster  was  pointed  out  in  an  earlier  paper  (Metz,  1918). 
This  was  extended  to  include  crossveinless  by  Weinstein  (1920);  and 
it  may  now  be  enlarged  by  the  addition  of  singed,  as  suggested  above. 
When  this  is  done  and  the  X-ehromosome  maps  of  the  two  species 
are  compared,  the  sequence  and  relative  positions  of  the  four  loci 
agree  as  closely  as  would  be  expected  if  the  characters  were  known 
to  be  homologues.  These  relations  are  indicated  in  figure  15. 
The  two  outside  maps  in  this  figure  are  drawn  to  the  same  scale; 
but  since  the  mrilis  map  is  considerably  longer  than  that  of  mela- 
nogaster (due  presumably  to  a  greater  amount  of  crossing-over  in 
this  species),  the  relative  positions  of  the  genes  are  shown  better  by 
making  the  maps  the  same  length.  For  this  reason  the  melanogaster 
map  is  represented  twice,  the  right-hand  one  being  drawn  to  a  dif- 
ferent scale,  to  equal  that  of  virilis. 

Another  case  of  close  resemblance  is  found  in  the  allelomorphs 
glazed  and  wax  compared  with  the  allelomorphs  lozenge  and  lozenge-2 
in  melanogaster,  as  discussed  above  under  wax  (p.  19).  The  map 
order  here  is  very  different,  however.  The  locus  of  glazed  and  wax 
is  near  the  end  of  the  map  (102),  while  that  of  lozenge  is  near  the 
middle  (28).  The  third  allelomorph,  rugose,  in  virilis  is  not  repre- 
sented in  inelanog aster.  Perhaps  the  resemblance  in  the  two  species 
is  accidental,  but  the  similarity  in  appearance  and  in  the  sterilit}', 
or  tendency  toward  sterility,  of  the  females,  suggests  homology, 
and  this  in  turn  suggests  a  rearrangement  of  genes. 

Of  the  other  sex-linked  characters,  however,  none  parallels  any 
in  melanogaster  sufficiently  to  make  homology  very  probable.  Sepia 
resembles  prune  in  melanogaster,  and  its  locus  is  near  that  of  yellow, 
as  in  melanogaster,  but  it  is  on  the  opposite  side  of  yellow.  If  the 
two  are  homologous  they  apparently  indicate  a  rearrangement  of 
genes.  The  case  of  magenta  in  virilis  and  garnet  in  melanogaster 
is  similar.  The  characters  are  somewhat  alike,  but  the  map  location 
does  not  correspond  very  closely,  although  the  order  of  genes  is  the 
same.  The  great  difficulty  in  both  of  these  cases  is  that  the  charac- 
ters are  not  sufficiently  reliable  for  comparison.  If  they  were 
distinguished  by  a  combination  of  features,  instead  of  merely  by 
the  possession  of  darker  eyes  than  usual,  the  case  would  be  more 
plausible.  This  is  especially  true  in  view  of  the  radical  difference 
between  the  "normal"  eye-colors  in  the  two  species  and  the  fact 
that  several  dark-eyed  mutants  are  known  in  each. 

Much  the  same  argument  may  be  used  in  the  case  of  vermilion 
virilis  and  vermilion  melanogaster,  vesiculated  virilis  and  inflated 
melanogaster  and  droop  virilis  and  depressed  melanogaster;  hence  it 
seems  unnecessary  to  give  a  detailed  discussion  of  these.     Their 


64 


Comparison  of  Characters 


factorial  relations  are  shown  on  the  accompanying  chromosome 
maps  (fig.  16),  with  the  exception  of  depressed,  which  is  an  autosomal 
character. 

Comparison  with  Sex-Linked  Characters  in  Drosophila  simulans. 

Turning  to  the  sex-linked  characters  of  other  species  than  mela- 
nogaster,  we  find  first  the  parallels  yellow  and  forked  in  D.  simulans. 
Since  these  are  homologous  to  the  yellow  and  forked  in  melanog aster 
the  above  discussion  covers  their 
case.  A  third  character,  bubble,  in 
simulans  parallels  vesiculated  in 
virilis  both  in  appearance  and  in  its 
map  locus.  This  type  of  character, 
like  many  of  the  eye-colors,  is  not 
very  reliable  for  comparison,  but, 
so  far  as  the  evidence  goes,  it  points 
towards  homology. 


D.  melanogaster 


D.  virilis 


0.    -- 


13.2 


21.0  -~ 


Comparison  with  Sex-Linked  Char- 
acters in  D.  willistoni. 


56.5  --, 


70.0 


—  yellow^ 


71 


forked' 


In  D.  willistoni,  the  four  char- 
acters yellow,  vermilion  (unpub- 
lished), forked,  and  stubby  resem- 
ble, respectively,  yellow,  vermilion, 
singed,  and  forked  in  virilis,  and  the 
order  and  relative  positions  of  their 
loci  on  the  map  are  similar,  except 
that  in  willistoni  the  series  begins 
(with  yellow)  at  approximately  the 
middle  of  the  map  instead  of  at  the 
end.  The  latter  fact  has  suggested 
(of.  Lancefield  and  Metz,  1922)  that 
the  large,  V-shaped  X  chromosome 
of  willistoni  may  represent  the  rod- 
like X  of  melanogaster  and  virilis 
plus  another  rod  of  equal  length  at- 
tached at  its  end.  This  is  in  agree- 
ment with  the  apparent  chromoso- 
mal relations  of  these  species,  and 
with  the  interpretation  given  by  D. 
E.  Lancefield  for  similar  conditions 
in  D.  ohscura.  A  sex-linked  ''crossveinless"  has  also  been  found 
recently  in  willistoni,  and  its  locus  is  very  close  to  that  of  vermiUon, 
as  is  the  case  in  virilis.  Whether  it  is  above  or  below  vermilion  has 
not  yet  been  determined.     It  will  be  recalled  that  the  vermilion 


--     6 


crossveinless.. 


~--  24 


singed.. 


--  42 


109 


Figure  15. 

X-chromosome  maps  of  Drosophila  melano- 
gaster and  D.  virilis,  indicating  loci  of     ^ 
"parallels"  (see  text). 


In  Different  Species.  65 

melanogaster  does  not  agree  in  position  (with  respect  to  yellow,  etc.) 
with  the  vermihon  in  virilis  (see  fig.  16).  In  the  former  it  is  between 
singed  and  forked,  while  in  the  latter  it  is  between  crossveinless  and 
singed,  at  a  point  very  close  to  crossveinless.  The  order  in  willistoni 
agrees  with  that  in  virilis,  suggesting  that  in  these  the  vermilions 
may  be  homologous.  If  crossveinless  in  willistoni  should  prove 
to  be  "located"  between  yellow^  and  vermilion,  the  parallehsm  would 
be  complete.^ 

The  only  other  case  of  close  resemblance  between  sex-linked 
characters  in  these  two  species  is  that  of  short.  Short  virilis  is 
similar  to,  but  less  extreme  than,  the  least  extreme  of  the  short 
allelomorphs  in  willistoni  (cf.  Lancefield  and  Metz,  1922,  fig.  13). 
Its  locus  with  respect  to  the  other  characters  considered  above, 
however,  is  very  different  (fig.  16).  This  indicates  that  the  two  are 
merely  mimics  or  else  that  a  rearrangement  of  genes  is  probably 
involved.  The  former  interpretation  seems  more  probable,  for 
mutants  with  short  veins  appear  frequently — indeed  a  second 
"short"  is  now  known  in  willistoni  which  is  due  to  a  mutation  in 
another  locus  in  the  X  chromosome  (unpublished  data). 

Comparison  with  Sex-Linked  Characters  in  Drosophila  obscura. 

(Figure  16.) 

When  the  sex-linked  characters  of  D.  ohscura  are  considered  in 
relation  to  those  of  virilis,  two  different  comparisons  may  be  made, 
according  to  the  manner  of  orientation  of  the  map.  These  have 
been  discussed  by  D,  E.  Lancefield  (1922,  p.  377),  and  need  only  a 
brief  review  here.  Yellow,  vermilion,  and  singed  are  fairly  similar  in 
the  two  species  and  their  loci  are  in  the  same  sequence.  It  is  also 
the  same  sequence  as  that  of  yellow,  vermilion,  and  forked  (probably 
singed)  in  willistoni.  The  map-distances  in  the  three  species  differ 
considerably,  but  this  appears  to  be  correlated  with  general  differ- 
ences in  crossing-over  in  the  three.  The  parallelism  of  these  series 
is  suggestive  of  homology  throughout,  especially  since  an  additional 
character,  scute,  is  present  and  coincides  in  its  locus  in  ohscura  and 
willistoni.  The  case  for  willistoni  and  obscura  is  further  strengthened 
by  the  fact  that  both  possess  V-shaped  X  chromosomes  and  that 
the  series  begins  (with  scute  and  yellow)  at  approximately  the 
middle  of  the  map. 

The  alternative  comparison  of  the  virilis  and  obscura  sex-linked 
groups  is  based  on  the  resemblance  between  the  two  "glazed" 
characters.  Glazed  in  obscura  agrees  with  glazed  in  virilis  both  in 
appearance  and  in  the  sterility  of  the  females.  If  these  characters 
are  considered  as  parallels,  it  is  necessary  to  reorient  the  maps  or  to 

*  Subsequent  data  indicate  that  this  is  the  case. 


66  Comparison  of  Characters 

postulate  some  rearrangement  of  loci,  for  with  the  above  orientation 
of  the  maps  glazed  lies  near  the  upper  end  in  one  case  and  the  lower 
end  in  the  other. 

In  both  of  these  comparisons  the  character  "short"  has  been 
omitted  because  it  is  so  unreliable  for  comparative  purposes  (see 
above,  under  willistoni).  It  is  similar  in  the  two  species,  however, 
and  the  sequence  of  loci  is  the  same  when  the  maps  are  oriented 
with  respect  to  yellow,  vermilion,  and  singed.  But  the  short  locus 
is  much  farther  from  the  others  than  it  is  in  virilis.  Stubby  in  obscura, 
with  a  locus  close  to  that  of  short,  has  also  been  omitted,  although  it 
might  be  compared  with  forked  in  virilis.  The  difficulty  here  is 
that  stubby  does  not  have  forked  bristles,  and  consequently  may  not 
be  in  the  same  category  as  the  "forked"  and  "singed"  characters. 
(See  special  discussion  of  these  above.) 

Comparison  with  Sex-Linked  Characters  in  Drosophila  funebris. 

Comparison  with  the  remaining  species,  D.  funebris,  involves  only 
the  character  forked.  As  pointed  out  by  Sturtevant  (1921a,  p.  63), 
and  as  noted  above,  forked  in  funebris  bears  a  close  resemblance  to 
forked  in  virilis.  It  might  also  be  compared  with  singed,  however, 
and  since  there  are  no  other  apparent  parallels  with  which  to  con- 
struct a  series,  both  possibilities  must  be  considered. 

COMPARISON  OF  AUTOSOMAL  CHARACTERS. 

As  might  be  expected  from  the  small  number  involved,  the  auto- 
somal characters  of  D.  virilis  include  too  few  "parallels,"  as  yet, 
to  permit  of  a  detailed  comparison  of  the  linkage  groups  with  those 
in  the  other  species.  Hence  the  following  considerations  are  given 
mainly  for  the  sake  of  completeness. 

The  resemblance  between  confluent  in  virilis  and  melanogaster 
has  been  pointed  out  in  previous  papers  (see  under  description  of 
confluent).  The  probability  of  homology  here  is  reduced  somewhat 
by  the  fact  that  dominant  characters  of  this  type  appear  to  be  fairly 
common.  Triangle  in  virilis,  for  instance,  is  similar  to  confluent, 
although  less  extreme  and  not  lethal  when  homozygous.  Extra  also 
resembles  confluent  in  some  cases.  The  veins  affected  by  confluent 
seem  to  be  particularly  susceptible  to  modification  in  this  direction. 

In  D.  obscura  a  dominant,  autosomal  confluent  is  known  (unpub- 
lished data  of  D.  E.  Lancefield),  but  this  is  much  more  extreme  than 
those  in  virilis  and  melanogaster  and  involves  other  veins.  It  is 
improbable  that  this  is  homologous  to  either  of  the  others. 

Concave  in  virilis  bears  a  close  resemblance  to  crumpled  in  mela- 
nogaster, and  gives  perhaps  the  most  convincing  evidence  of  homology. 
Both  characters  are  autosomal  recessives;  both  affect  the  scutellar 
bristles  and  the  hairs  on  the  arista  in  the  same  fashion;  and  both 


In  Different  Species.  67 

involve  an  irregular  series  of  wing  modifications  that  ranges  from  the 
normal  condition  through  various  long,  narrow,  curved,  or  shortened 
forms  (see  figs.  5  to  7  in  plate  3)  to  a  condition  in  which  the  wing  is 
very  short  and  broad  and  is  wavy  or  crumpled.  In  both  cases  the 
wings  are  frequently  asymmetrical  and  are  often  held  at  an  angle 
from  the  body.  Crumpled  is  in  the  third-chromosome  series  in 
melanogaster  at  approximately  93  (unpublished  data  of  C.  B.  Bridges), 
and  concave  is  in  the  second-chromosome  group  of  virilis  (fig.  7). 
If  we  consider  the  genes  homologous,  we  would  compare  the  virilis 
second-chromosome  group  with  the  third  of  melanogaster.  The 
only  other  third-chromosome  characters  that  resemble  any  in 
virilis  are  ascute  (at  about  the  middle  of  the  map)  and  spread  (at 
about  65).  The  latter  may  be  left  out  of  consideration  for  the 
present,  because  the  nature  of  the  character  makes  it  of  little  value 
for  comparison,  (i.  e.,  spread- wing  mutants  are  too  numerous). 
Ascute  resembles  hunch  in  virilis,  which  is  in  the  third-chromosome 
series.  This  suggests  that  chromosome  III  of  melanogaster  may 
represent  chromosomes  II  and  III  in  virilis  combined. 

The  presence  in  D.  ohscura,  however,  of  two  characters  like  ascute, 
in  different  linkage  groups,  casts  considerable  doubt  on  the  reliability 
of  ascute  for  comparative  purposes.  Likewise,  it  should  be  noted 
that  confluent  is  in  the  same  linkage  group  as  concave  in  virilis, 
while  the  characters  resembling  them  in  melanogaster  are  in  different 
groups  (II  and  III).  It  seems  probable  that  most  of  the  above 
cases  involve  mimicry  rather  than  homology. 

The  other  cases  of  resemblance  among  the  autosomal  characters 
are  equally  doubtful,  except  in  the  case  of  bent  and  net,  which  have 
been  discussed  fully  above  (pp.  51-53).  Telescoped  resembles  fur- 
rowed melanogaster  in  its  effect  on  the  thorax,  but  the  eyes  are  affected 
very  differently  in  the  two  cases,  and  the  bristles  are  short  in  furrowed 
and  not  in  telescoped,  so  that  the  resemblance  is  probably  superficial. 
A  closer  resemblance  is  shown  by  the  sex-linked  character  compressed 
in  D.  ohscura.  It  resembles  telescoped  in  nearly  all  respects  (see 
D.  E.  Lancefield,  1922).  This  resemblance  recalls  the  fact  that  hunch 
in  virilis  is  in  the  same  linkage  group  (III)  as  telescoped  and  that  in 
ohscura  ascute,  which  resembles  hunch,  is  sex-linked.  Thus  the 
two  sex-linked  characters  in  the  one  case  resemble  the  two  third- 
chromosome  characters  in  the  other,  suggesting  that  the  V-shaped 
X  chromosome  of  ohscura  represents  the  rod-like  X  of  virilis,  plus 
chromosome  III.  This  is  made  improbable,  however,  by  the  presence 
in  ohscura  of  an  autosomal  character  like  ascute,  and  also  by  the  fact 
that  the  loci  of  compressed  and  ascute  are  in  the  part  of  the  map 
that  seems  to  correspond  to  the  X-chromosome  map  of  virilis. 

Only  two  other  characters  need  be  noted  in  this  connection.  The 
first  of  these  is  approximated.     It  resembles  several  characters  in 


68  Comparison  of  Characters. 

melanog aster,  as  for  example,  dachsous  and  are,  but  each  of  the 
latter  involves  additional  modifications.  The  same  is  true  with 
respect  to  approximated  in  willistoni,  which  has  short  legs  hke 
dachsous.  The  second  character  is  broken.  This  resembles  cross- 
veinless,  or  characters  of  this  type  of  which  there  are  several  in  other 
species.  One  such  autosomal  character  is  known  in  obscura,  two  or 
three  are  known  in  willistoni  (one  being  sex-linked),  and  a  sex-hnked 
crossveinless  is  known  in  melanogaster  and  virilis. 


Vermilion.  69 

X.    THE  CASE  OF  VERMILION,  AND  THE  POSSIBILITY 
OF  A  REARRANGEMENT  OF  GENES. 

The  resemblance  between  virilis,  willistoni,  and  ohscura  in  respect 
to  the  location  of  vermilion,  and  their  consistent  difference  from 
melanogaster  in  this  feature,  have  already  been  pointed  out.  They 
suggest  that  the  vermilion  of  melanogaster  is  not  homologous  to  any 
of  the  others.  This  view  receives  some  support  from  the  obser- 
vations of  Lancefield  (1922,  p.  377)  on  ohscura,  showing  that  the 
double-recessive  eosin  vermilion  differs  from  the  eosin  vermilion  of 
melanogaster.  As  Dr.  Sturtevant  has  suggested  to  us,  however,  the 
fact  that  vermihon  is  a  frequently  appearing  mutant — at  least  in 
some  species — and  that  only  one  such  character  is  known  in  the 
sex-linked  group  of  any  of  the  above  species  supports  the  opposite 
view,  i.  e.,  that  the  same  gene  is  involved  throughout.  This  argu- 
ment may  be  questioned,  perhaps,  on  the  ground  that  vermilion 
(in  ohscura  and  melanogaster  at  least)  resembles  the  autosomal  char- 
acter scarlet  in  ohscura,  melanogaster,  and  simulans  (cf.  D.  E.  Lance- 
field, 1922,  p.  377),  but  such  an  objection  is  not  serious  enough  to 
rule  out  the  hypothesis.  There  are  other  cases  also  (e.  g.,  sepia, 
magenta,  wax,  vesiculated,  etc.),  as  noted  above,  involving  similar 
characters  but  a  different  map  order.  And  more  striking  examples 
are  known  in  other  species.  Sturtevant  (192 Id),  for  instance,  has 
presented  evidence  that  indicates  a  rearranged  map  order  in  the 
third  chromosome  of  D.  simulans  (as  compared  with  melanogaster) , 
where  the  homology  of  genes  has  been  tested  by  hybridization. 
Lancefield  (1922)  has  observed  a  similar  case  in  D.  ohscura,  although 
here  no  hybridization  tests  are  possible.  Both  of  these  cases  have 
been  discussed  by  the  authors  mentioned  and  the  details  need  not 
be  given  here.  The  most  probable  interpretation  of  the  results, 
at  least  in  the  case  of  D.  simulans,  would  seem  to  be  on  the  assumption 
of  a  rearrangement  of  genes,  brought  about  by  a  transposition  of 
part  of  a  chromosome.  And  this  is  the  interpretation  given  by 
Sturtevant  (1.  c). 

Recent  evidence  obtained  by  Dr.  H.  J.  IMuller,  however,  brings 
up  the  possibility  of  another  interpretation  for  cases  of  this  kind. 
In  a  paper  presented  before  the  American  Naturalists  at  the  Toronto 
meeting  (1921),^  Muller  described  the  results  of  experiments  with  a 
mutant  race  of  Drosophila  melanogaster  in  which  crossing-over  was 
greatly  reduced  by  a  "cross-over  modifier."  One  of  the  pecularities 
of  these  results  was  that  when  treated  in  the  ordinary  fashion  for  con- 
structing a  map  they  gave  a  reversed  order  of  loci  for  certain  well- 
known  characters.     This  was  apparently  due  to  an  excess  of  double 

1  "A  lethal  gene  which  changes  the  order  of  the  loci  in  the  chromosome  map."  The  title  of 
this  paper,  without  abstract,  is  printed  in  the  Anatomical  Record,  Jan.  1022,  23:129.  The 
present  reference  is  made  with  Dr.  Muller's  permission. 


70  Vermilion. 

cross-overs  over  singles.  In  any  case,  according  to  MuUer,  it  was 
not  due  to  a  chromosomal  reorganization,  as  was  shown  by  genetic 
test  in  cases  where  the  "cross-over  modifier"  was  eliminated. 

It  is  perhaps  too  early  to  draw  general  conclusions  from  this  and 
other  cases  involving  cross-over  modifiers,^  but  it  is  to  be  observed 
that  Muller's  case  gives  the  appearance  of  involving  a  rearrangement 
of  genes,  and  is  analogous  in  some  respects  to  the  case  of  vermilion 
just  cited  and  to  those  in  D.  simulans  and  D.  obscura.  Until  further 
evidence  is  obtained,  therefore,  it  is  necessary  to  consider  the  possi- 
bility of  an  inverted  sequence  of  loci  being  due  to  a  disturbance  in 
crossing-over  rather  than  to  an  actual  rearrangement  of  genes. 

'  Cf.  especially  MuUer  (1916)  and  Sturtevant  (1919).  In  Sturtevant's  table  17  (p.  320)  the 
three  cross-overs  involving  the  region  b— pr  were  all  doubles. 


Comparison  of  Maps.  71 

XI.     COMPARISON  OF  X-CHROMOSOME  MAPS. 

Taking  into  account  all,  or  practically  all,  of  the  characters  that 
bear  a  resemblance  to  one  another,  and  omitting  the  remainder, 
the  X-chromosome  maps  of  the  six  species  considered  above  aj)])oar 
as  shown  in  figure  16.  These  maps  are  all  drawn  to  the  same  scale, 
based  on  percentages  of  crossing-over.  The  first  three  represent 
X  chromosomes  of  the  short,  rod-like  tji^e;  the  third  and  fourth 
are  of  the  long  V-shaped  tj^pe;  and  the  last  (D.  funebris)  is  rod-like, 
but  uncertain  as  to  length  (see  p.  7).  Three  different  grades  of 
characters  are  represented  on  these  maps.  Characters  that  give 
considerable  indication  of  homology  to  one  or  more  of  the  others 
are  represented  by  words  beginning  with  capitals;  those  considered 
as  possible  but  not  probable  homologues  are  represented  in  small 
type;  while  the  remainder  are  represented  merely  by  marks  to  indicate 
their  respective  loci. 

The  alinement  of  the  maps  is  based  on  the  apparent  degree  of 
resemblance  of  the  characters  as  discussed  above.  One  of  the  most 
striking  features  noticeable  in  a  comparison  of  the  maps  is  shown  by 
the  relations  of  j'-ellow.  In  the  three  species  having  the  rod-like 
type  of  X  chromosome,  yellow  comes  at  or  near  the  end  of  the  map ; 
while  in  the  two  possessing  long  V-shaped  X  chromosomes  it  comes 
near  the  middle.  The  probability  of  homology  throughout  this 
series  is  supported  by  the  presence  in  three  species  of  a  very  closely 
linked  character  scute  ( =  scutellar) .  On  the  basis  of  this  resem- 
blance, the  maps  are  placed  so  that  the  locus  of  yellow  corresponds 
throughout,  except  in  the  case  of  the  funebris  map,  where  yellow  is 
not  represented.  The  latter  has  been  oriented  with  respect  to  notch 
and  forked  (see  Sturtevant,  1921a). 

If  we  compare  the  total  lengths  of  the  different  maps  (omitting 
funebris  on  account  of  the  small  number  of  loci),  and  consider  the 
size  relations  of  the  chromosomes  involved,  we  note  at  once  that  the 
maps  are  not  proportional  to  chromosome  length  in  all  cases.  If  we 
use  the  melanogaster  map  as  a  standard  of  comparison,  we  find  that  the 
simulans  map  agrees  fairly  closely,  but  that  the  mrilis  map  is  nearly 
50  per  cent  too  long.  Likewise,  the  obscwa  map,  which  should  be 
approximately  twice  as  long,  is  actually  about  three  times  as  long. 
The  willistoni  map,  on  the  other  hand,  is  much  too  short.  It  should 
be  approximately  double  that  of  melanogaster,  and  equal  to  that  of 
obscura;  but  instead  it  is  only  slightly  longer  than  that  of  melatiogaster. 

In  each  of  these  cases  (excluding /wnc6r/s)  the  number  of  characters 
studied  is  sufficient  to  make  it  probable  that  most  of  the  chromosome 
is  represented.  The  difference  appears  to  be  due,  therefore,  to  dif- 
ferences in  amount  of  crossing-over  in  the  various  s])ecies.  This 
interpretation  is  supported  also  by  the  distribution  of  the  loci  on  the 
maps.     In  willistoni,  where  crossing-over  is  presumed  to  be  low,  the 


72 


Comparison  of  Maps. 


loci  are  relatively  crowded  as  compared  with  those  of  virilis  and 
obscura,  in  which  almost  as  many  loci  are  represented.  The  dif- 
ferences seem  to  be  largely  due  to  general  increase  or  decrease  in 
crossing-over,  but  it  is  probable  that  some  regions  in  the  chromosomes 
differ  more  than  others  in  this  respect.  This  has  been  shown  to  be 
the  case  in  D.  simulans  (Sturtevant,  1921a),  and  is  indicated  in  the 


D.willistoni     D. obscura 


■  -short 


0.  simulans 


D.virilis 


O.melanogaster 


Yellow  — 
-  Prune  ^^ 

Rubyoid- 
bubble 


Carmine - 


Forked  - 


Scute., 
,  xYellow, 
irPrune 
<White 

Notch 

Ruby 


Crossveinless, 

Singed, 

■lozenge     »_ 
--Vermilion 

Garnet 


inflated 
Forked, 


sepia 

VVnow- 


Crossveinless . 
4^  Vermilion     / 
esiculated' 


'■-Singed' 


Scute-. 
.Veiiow- 


Vecmilion 


■  Forked  ^ 


-Stubby 


•magenta'      ,-' 
'•}■  Forked" 


short 


glazed 
droop 


O.funebrJs 


Scutellar 
''Jfellow 

Notch 
vvh.te 


-  -Vermilion 
-Singed  ' 


Notch 


Forked 


stubby  ' 
-  -short 
stubby' 


Figure  16. — X-chromosome  maps  of  six  species  of  Drosophila  drawn  to  scale 
according  to  cross-over  percentages. 


Sex-Chromosome  Maps. 


73 


others  by  the  spacing  of  the  loci  in  clusters,  with  intermediate 
regions  almost  blank.  Such  regions  show  relatively  little  conformity 
in  the  different  species.  If  the  cases  of  parallel  characters  are  reliable, 
they  furnish  more  definite  information,  but  we  do  not  consider  it 
safe  to  base  any  detailed  comparison  on  this  ground  at  present. 
The  relations  are  easily  seen  by  an  examination  of  figure  16. 

D.willistoni 


D.obscura 

-glazed 


■  short 


D.simulans  D.virilis 

D.melanogaster 


.  .Yellow- 
Prune - 


■  -Rubyoid' 


■  -bubble 


Crossveinless-' " " 

-■Singed- ., 


Carmine 


i  Forked 


1 


, Scute  - - 
:^  Yellow. 
^ Prune 
\White 

Notch 
-Ruby 


lozenge 
-  -Vermilion 


-  -Garnet 


nflated' 
■  Forked- 


sepia 
Yellow: 


,Crossveinless 

Vermilion 

vesiculated 


Vermilion 


-■Forked- 


-Singed- '' 


-.magenta 
,-  -  Forked, 


■  short       \ 

I 
\ 

■  glazed  wax'' 

■  ■droop 


Scute-.. 

-Yellow- - 


^cutellar 
-Yellow 

Notch 

White 

Vermilion 
Singed  ' 


'Stubby 


stubby  ? 
-short 
stubby? 

Figure  17. — The  same  maps  as  those  shown  in  figure  16.  but  drawn  to  different  scales  in 

accordance  with  chromosome  length. 


74  Comparison  of  Maps. 

In  figure  17  we  have  represented  the  same  maps  as  shown  in  figure 
16,  but  drawn  to  different  scales,  so  that  they  are  roughly  propor- 
tional to  the  lengths  of  the  respective  chromosomes.  This  tends  to 
eliminate  the  differences  due  to  any  general  increase  or  decrease  in 
crossing-over,  but  of  course  it  does  not  eliminate  differences  that 
affect  particular  regions. 

A  comparison  of  these  maps  shows  a  degree  of  conformity  between 
the  loci  of  possible  "parallels"  that  harmonizes  in  most  cases  with 
the  view  that  they  may  be  homologous.  There  is,  of  course,  a 
considerable  element  of  chance  entering  in  here,  and  some  of  the 
resemblances  may  be  accidental,  but  they  can  hardly  all  be  accounted 
for  on  this  basis. 

The  autosomal  maps  of  D.  virilis  are  not  yet  sufficiently  reliable 
for  comparison.  In  considering  rates  of  crossing-over,  however, 
we  may  compare  the  X  chromosome  map  of  virilis  with  the  autosomal 
maps  of  D.  melanogaster  (the  only  ones  available  for  the  purpose). 
When  this  is  done  we  find  the  same  sort  of  difference  as  noted  in 
the  case  of  the  X  chromosomes  of  the  two  species,  i.  e.,  crossing-over 
is  more  frequent  in  virilis.  The  X-chromosome  map  of  virilis  slightly 
exceeds  both  of  the  long  autosomal  maps  in  melanogaster,  although 
the  autosomes  themselves  are  both  of  the  long  V-shaped  type,  approxi- 
mately twice  as  long  as  the  rod-like  X  chromosome  of  virilis. 


Coincidence. 


75 


XII.     COINCIDENCE. 

Coincidence  in  the  X  chromosome  of  D.  virilis  appears  to  resemble 
that  in  D.  melanogaster,  as  has  already  been  noted  by  Weinstein 
(1920).  Since  this  subject  is  being  investigated  in  detail  by  Dr. 
Weinstein,  we  will  confine  ourselves  to  a  tabulation  of  the  values 
obtained  from  the  new  data  in  the  present  paper.  In  most  cases  the 
numbers  are  not  large  enough  to  be  satisfactory,  but  the  results 
agree  with  previous  ones  in  indicating  a  resemblance  to  those  obtained 
from  D.  melanogaster. 


Table  8. — Coincidence  in 

Drosophila  virilis. 

Experiment. 

Regions 
involved. 

Total 
flies. 

Double 
cross-overs. 

Calculated          Map-         „  .     .  , 
distance.         distance. 

34,48 

48 

48 

34,48 

48 

34,  35,  48 

20,  36.  46 

46,47 

38,  39,  47 

46,47 

38,  39,  47 

40,  46 

40,46 

48 

34,48 

48 

48 

27,40,41,42 

43,  44,  46,  47 

48 

43,  44,  47 

38,  39,  47 

45,48 

45,48 

45,48 

43,  44,  47 

32 

33 

se-c-si 

se-c  si-m 

se-c  si-f 

se-c  si-s 

se-c  f-3 

se-c-s 

y-e-v 

y-v(vs)-m.. . 

y-vs-f 

y-v(vs)  m-f.. 

y-vs  f-r 

c-v-m 

c-v  m-f 

c-si-m 

c-si-s 

c-si  m-f 

c-si  f-3 

V   —m-f 

vs. 

vs-m  f-r ...  . 

vs-f-r 

si-m-f 

si-m  f-s 

m-f-s 

m-f-r 

t-s-d 

s-r-d 

547 
406 
406 
547 
406 
972 
1,506 
999 
980 
999 
980 
2,050 
2,050 
406 
547 
406 
406 

5,218 

2,068 
980 
577 
577 
577 

2,068 
315 
409 

16 
22 
22 
34 

8 
81 

2 
51 
61 

3 
36 

3 

0 
12 
29 

1 

9 

73 

168 

104 

7 

31 

9 

29 

2 

19 

35 
61 
64 
81 
82 
74 
20 
53 
55 
56 
86 
37 
39 
42 
62 
45 
63 

39 

65 
67 
32 
50 
22 
31 
25 
34 

42 
67 
71 
86 
86 
86 
18 
61 
65 
65 
96 
43 
47 
43 
62 
57 
62 

46 

77 
77 
29 
44 
19 
35 
28 
23 

0.997 

1.031 

1.004 

0.882 

0.585 

1.002 

1.276 

0.777 

0.945 

0.515 

0.598 

0.824 

0.0 

0.749 

0  982 
0.548 
0.878 

1  124 

0  927 
0.996 
1.239 
1.025 
2.426 
1.042 
0.646 
1.654 

In  table  8  the  data  are  given  in  order,  according  to  the  map  region 
involved,  beginning  with  the  uppermost  loci.  The  cases  involving 
more  than  25  double  cross-overs  and  more  than  900  flies  are  sum- 
marized separately  in  table  9,  and  are  arranged  in  accordance  with 
map-distance  rather  than  map-region.  In  both  tables  the  column 
headed  "Calculated  distance"  gives  the  "distance"  between  the 
uppermost  and  lowermost  loci,  calculated  from  the  particular 
experiments  involved.  Under  "Map-distance"  is  given  the  cor- 
responding value  taken  from  the  final  map  (fig.  7).  The  latter  is 
the  larger  value  in  most  cases. 


76  Coincidence. 

Table  9. — Coincidence  in  Drosophila  virilis  (selected  data  from  table  8.) 


Experiment. 

Regions          Total 
involved.         flies. 

Double 
cross-overs. 

Calculated 
distance. 

Map- 
distance. 

Coincidence. 

43.  44.  47 

27,  40,  41,  42 

43,  44,  46,  47 

48 

46,  47 

38,  39,  47 

43,  44,  47 

38,  39,  47 

34,  35,  48 

38,  39,  47 

m-f-r 

c  ] 

V  [-m-f 

vsJ 
y-v(vs)-m. . . 

y-vs-f 

vs-m  f-r.  .  .  . 

vs-f-r 

se-c-s 

y-vs  f-r 

2,068 

5,218 

999 
980 
2,068 
980 
972 
980 

29 

73 

51 
61 
168 
104 
81 
36 

31 

39 

53 
55 
65 
67 
74 
86 

35 

46 

61 
65 
77 
77 
86 
96 

1.042 

1.124 

0.777 
0.945 
0.927 
0.996 
1.002 
0.598 

Since  the  loci  of  crossveinless,  vermilion,  and  vesiculated  are  so 
close  together,  data  from  experiments  involving  these  characters 
have  been  lumped  together  in  some  cases  (e.  g.,  the  second  case  in 
table  9),  in  order  to  secure  larger  numbers  for  the  calculations. 
This  introduces  a  shght  error,  but  one  that  may  safely  be  ignored  for 
present  purposes. 


Chromosomes  and  Linkage  Groups.  77 

XIII.     CHROMOSOMES  AND  LINKAGE 
GROUPS  COMPARED. 

On  the  basis  of  its  chromosomes,  Drosophila  virilis  would  be  expected 
to  possess  six  groups  of  linked  genes.  Five  of  these,  including  the 
sex-linked  group,  should  be  of  approximately  the  same  size  as  regards 
amount  of  crossing-over,  and  the  sixth  should  be  relatively  very 
small,  both  in  respect  to  amount  of  crossing-over  and  to  number  of 
genes.  Six  groups  have  been  identified,  as  indicated  in  the  above 
account.  Of  these  the  sex-hnked  group  (group  I)  includes  far  more 
genes  than  any  of  the  others,  as  would  be  anticipated  from  the  fact 
that  sex-linked  mutations  are  more  readily  detected  than  autosomal 
ones.  The  autosomal  Unkage  groups  (II-VI)  contain  respectively 
4,  6,  3,  5,  and  2  characters,  and  do  not,  as  yet,  show  the  expected 
difference  distinguishing  one  group  from  the  other  four.  As  to 
amount  of  crossing-over,  it  is  too  early  to  compare  them,  except  in 
a  general  way.  Groups  II,  III,  and  V  show  sufficient  crossing-over 
to  indicate  that  they  will  probably  equal  the  sex-hnked  group  in 
map-length  when  more  characters  are  obtained.  On  this  basis, 
these  four  groups  (I,  II,  III,  and  V)  are  identified  with  four  of  the 
large  chromosomes.  Groups  IV  and  VI,  however,  although  con- 
taining 3  and  2  characters,  respectively,  give  no  crossing-over, 
and  the  question  arises  as  to  which  is  to  be  identified  with  the  re- 
maining large  chromosome  and  which  with  the  small  ???-chroniosome. 
This  question  can  not  be  answered  with  certainty  at  present,  but 
the  following  three  lines  of  e\'idence  favor  the  view  that  group 
VI  represents  the  ?72-chromosome :  (1)  One  of  its  two  characters 
appears  to  be  a  deficiency  for  the  other,  indicating  that  a  small 
''region"  is  involved.  (2)  Both  characters  resemble  characters 
in  group  IV  (representing  the  7?i-chromosome)  of  D.  inelanogaster 
(see  above  under  group  VI).  (3)  The  absence  of  crossing-over 
in  group  IV  of  virilis  may  possibly  be  due  to  the  fact  that  the  char- 
acters involved  have  arisen  in  stocks  obtained  from  different  localities 
(see  above  under  group  IV).  Possibly  the  "fourth"  chromosomes 
in  these  stocks  are  sufficiently  different  to  inhibit  crossing-over. 
An  attempt  is  being  made  to  test  this  view.  Another  explanation  is 
that  group  IV  represents  a  long  chromosome,  and  that  crossing- 
over  is  infrequent  in  this  chromosome  because  of  the  presence 
of  one  or  more  genes  reducing  crossing-over,  analogous  to  those  known 
to  have  this  effect  in  certain  races  of  D.  inelanogaster  (Muller,  1916; 
Sturtevant,  1919;  Detlefsen,  1920;  Gowen  and  Gowen,  1922). 

In  the  other  species  of  Drosophila,  exclusive  of  inelanogaster  and 
simulans,  Uttle  has  been  published  regarding  the  autosomal  linkage 
groups.  It  may  be  stated,  however,  that  in  both  willistoni  and 
obscura  the  number  of  such  groups  agrees  with  or  at  least  does  not 


78  Chromosomes  and  Linkage  Groups. 

exceed  the  haploid  number  of  autosomes.  In  loillistoni,  which  has 
only  two  pairs  of  autosomes  (unless  the  m-chromosomes  are  present 
but  are  so  small  as  to  have  escaped  detection),  only  two  groups  of 
non-sex-linked  characters  have  been  found.  One  of  these  contains 
eight  characters  and  gives  a  long  map;  the  other  contains  six  char- 
acters, but  their  linkage  relations  are  not  yet  worked  out. 

In  ohscura  where  four  pairs  of  autosomes  are  represented,  two 
autosomal  linkage  groups  with  four  or  more  characters  each,  are 
known;  and  preliminary  results  indicate  that  the  other  two  are  prob- 
ably represented  by  one  character  each  (unpublished  data  of  D.  E. 
Lancefield). 

In  D.  melanog aster,  as  is  well  known,  the  four  linkage  groups  show 
a  fairly  close  correspondence  to  the  four  pairs  of  chromosomes,  both 
as  regards  number  of  loci  and  amount  of  crossing-over.  In  the 
other  species  (at  least  simulans,  virilis,  and  willistoni)  the  evidence 
points  in  the  same  direction. 


D.  H.  HILL  LIBRARY 


Tabulation  of  Data. 


79 


XIV.     TABULATION  OF  LINKAGE  EXPERIMENTS. 

Linkage  Experiments  on  Sex-Linked  Genes  (Group  1). 

(Experiments  1  to  53.) 


Exp.  1. — Sepia  vermilion. 
Mating:  sepia  X  vermilion. 
6  cultures  (E  625-6,  535-6,  545-6). 

Non-cross-overs  (se  191;  v  226)    417 

Cross-overs  (se  v  60;  -f  68) 128 


Total 

Per  cent  cross-overs,  se-v,  23.5. 


545 


Exp.  2. — Frayed  forked. 
Mating:  frayed  X  forked. 
3  cultures  (V  812.  815,  827). 

Non-cross-overs  (fd  72;  f  61)    133 

Cross-overs  (fd  f  47;  -h  74) 121 

Total 254 

Per  cent  cross-overs,  fd— f,  47.6. 

Exp.  3. — Yellow  crossveinless. 
Mating:  yellow  crossveinless  X  wild-type. 
5  cultures  (P  833-837). 

Non-cross-overs  (y  c  159;  +  161) 320 

Cross-overs  (y  40 ;  c  46) 86 


Total 

Per  cent  cross-overs,  y— c,  21.2. 


406 


Exp.  4. — Yellow  vermilion. 

Mating:  yellow  X  vermilion. 

6  cultures  (P  656,  681,  693-4,  722.  725). 

Non-cross-overs  (y  176;  v  167) 343 

Cross-overs  (y  v  44 ;  +  45) 89 

Total 432 

Per  cent  cross-overs,  y-v.  20.6. 

Exp.  5. — Vermilion  vesiculated. 

Mating:  vermilion  X  vesiculated. 

7  cultures  (E  447-8,  473,  735-6,  747-8). 

Non-cross-overs  (v  481 ;  vs  463) 944 

Cross-overs  (v  vs  9;  -|-  14) 23 

Total 967 

Per    cent    cross-overs,   v— vs    2.4;    counting 
only  vs,  1.9. 

Exp.  6. — Vermilion  ringed. 

Mating:  vermilion  X  singed. 

9  cultures  (P  529-532,  538,  553,  682,  736-7). 

Non-cross-overs  (v  344;  si  309) 653 

Cross-overs  (v  si  75;  -f  74) 149 

Total 802 

Per  cent  cross-overs,  v— si  18.6. 

Exp.  7. — Vermilion  short. 

Mating:  vermilion  X  short. 
14   cultures   (P  543-7.  551-2.  562-5.    M   40, 
42,  62). 

Non-cross-overs  (v  489;  s  450) 939 

Cross-overs  (vs  344;  +  370) 714 


Total 

Per  cent  crose-overs,  v— a  43.2. 


.1.653 


Exp.  8. — Vermilion  triangle. 
Mating:  vermilion  X  triangle. 
3  cultures  (E  410-11.  446). 

Non-cross-overs  (v  59;  T  43) 102 

Cross-overs  (v  T  13 ;  -f  52) 65 


Total 

Per  cent  cross-overs.  v-T  38.9. 


167 


Exp.  9. — Vermilion  glazed. 
Mating:  vermilion  X  glazed. 
6  cultures  (L  541.  541  (1).  E  166.  179,  347-S). 

Non-cross-overs  (v  70;  r«  45) 115 

Cross-overs  (v  r"  30;  -|-  55) 85 


Total 

Per  cent  cross-over,  v— r»  42.5. 


200 


Exp.   10. — Singed  triangle. 
Mating:  singed  X  triangle. 

4  cultures  (M  27.  30.  32.  52). 

Non-cross-overs  (si  38;  T  44) 82 

Cross-overs  (si  T  18;  +  36) 54 

Total 136 

Per  cent  cross-overs,  si-T  39.7. 

Exp.  11. — Singed  short. 
Mating:  singed  X  short. 

8  cultures  (P  643-4,  650,  672-3.  704.  M  91. 
1246). 

Non-cross-overs  (si  176;  a  159) 335 

Cross-overs  (si  s  97;  +  119) 216 

Total 551 

Per  cent  cross-overs,  si-s  39.2. 

Exp.  12. — Singed  droop. 

Mating:  singed  X  droop. 
2  cultures  (M  44,  50). 

Non-cross-overs  (si  26;  d  17) 43 

Cross-overs  (si  d  12 ;  +  25) 37 

Total 80 

Per    cent   cross-overs,  si-d   46.2;    counting 
only  d  flies  41.3. 

Exp.  13. — Triangle  short. 

Mating:  triangle  X  short. 

5  cultures  (M  41.  51.  64.  122.  198). 

Non-cross-ovcrs  (T  152;  s  124) 276 

Cross-overs  (T  s  8;  +  8) 16 

Total 292 

Per  cent  cross-overs.  T— a  5.5. 

Exp.   14. — Triangle  rugose. 

Mating:  triangle  X    rugose. 
2  cultures  (L  681.  690). 

Non-cross-ovcrs  (T  72;  r  81) 153 

Cross-overs  (T  r  7;  -f-  8) 15 

Total 16S 

Per  cent  cross-overs,  T-r  8.9. 


80 


Tabulation  of  Data. 


Exp.  15. — Triangle  droop. 

Mating:  triangle  X  droop. 
3  cultures  (M  43,  45,  63). 

Non-cross-overs  (T  68;  d  55) 123 

Cross-overs  (T  d  17;  M-  51) 68 

Total 191 

Per    cent    cross-overs,   T-d   23.6,    counting 
only  d  flies. 

Exp.  16. — Short  rugose. 

Mating:  short  X  rugose. 

7  cultures  (P  533-4,  539,  555-8). 

Non-cross-overs  (s  327;  r  270) 597 

Cross-overs  (s  r  57;  -f-  76) 133 

Total 730 

Per  cent  cross-overs,  s-r  18.2. 

Exp.  17. — Short  droop. 

Mating:  short  X  droop. 
3  cultures  (M  38,  96,  100). 

Non-cross-overs  (s  93;  d  48) 141 

Cross-overs  (s  d  8 ;  -|-  47) 55 

Total 196 

Per    cent    cross-overs,    s-d  28.0;    counting 
only  d  flies,  14.3. 

Exp.  18. — Rugose  droop. 

Mating:  rugose  X  droop. 

8  cultures  (E  1260-2,  1307-8,  1349-51). 

Non-cross-overs  (d  283;  r  314) 597 

Cross-overs  (d  r  23 ;  -f  68) 91 

Total 688 

Per    cent    cross-overs,  r— d,    counting    only 
d.  7.5. 

Exp.  19. — Sepia  yellow  crossveinless. 
Mating:  sepia  X  yellow  crossveinless. 
7  cultures  (L  492,  495-6,  E  528-9,  547-8). 

Non-cross-overs  (se  204;  y  c  206) 410 

Co.  region  1  (se  y  c  8;  -H  16) 24 

Co.  region  2  (se  c  53 ;  y  54) 107 

Co.  region  1-2  (se  y  2 ;  c  5) 7 

Total 548 

Per  cent  cross-overs,  se-y  5.6;  y— c  20.8. 

Exp.  20. — Yellow  crossveinless  vermilion. 

Mating:  yellow  crossveinless  X  vermilion. 
3  cultures  (E  409,  744,  746). 

Non-cross-overs  (y  c  177;  v  197) 374 

Co.  region  1  (y  v  59;  c  37) 96 

Co.  region  2  (y  c  v  1 ;  -f  1) 2 

Total 472 

Per  cent  cross-overs,  y— c  20.3,  c-v  0.4. 

Exp.  21. — Yellow  crossveinless  singed. 
Mating:  yellow  crossveinless  X  singed. 
5  cultures  (P  498,  508-11). 

Non-cross-overs  (y  c  148;  si  135) 283 

Co.  region  1  (y  si  28;  c  36) 64 

Co.  region  2  (y  c  ei  23 ;  4-  40) 63 

Co.  region  1-2  (y  5;  c  si  2) 7 

Total 417 

Per  cent  cross-overs,  y— c  17.0;  o-si  16.8. 


Exp.  22. — Yellow  crossveinless  short. 

Mating:  yellow  crossveinless  X  short. 
1  culture  (P  567). 

Non-cross-overs  (y  c  34;  s  27) 61 

Co.  region  1  (y  s  7 ;  c  8) 15 

Co.  region  2  (y  c  s  26;  -|-  26) 52 

Co.  region  1-2  (y  4;  c  s  5) 9 

Total 137 

Per  cent  cross-overs,  y— c  17.5;  c-s  44.5. 

Exp.  23. — Yellow  crossveinless  droop. 

Mating:  yellow  crossveinless  X  droop. 
1  culture  (E  1314). 

Non-cross-overs  (y  c  28;  d  15) 43 

Co.  region  1  (y  d  1 ;  c  4) 5 

Co.  region  2  (y  c  d  5;  +  15) 20 

Co.  regioa  1-2  (y  10;  c  d  1) 11 

Total 79 

Per  cent  cross-overs,  y— c  20.2;  c-d  39.2. 

Exp.  24. — Yellow  vermilion  short. 

Mating:  yellow  short  X  vermilion. 
4  cultures  (P  707-8,  710,  712). 

Non-cross-overs  (y  s  56;  v  65) 121 

Co.  region  1  (y  v  9;  s  11) 20 

Co.  region  2  (y  43 ;  v  s  29) 72 

Co.  region  1-2  (y  v  s  5;  -[-  7) 12 

Total 225 

Per  cent  cross-overs,  y-v  14.2;  v-s  37.3. 

Exp.  25. — Yellow  singed  short. 

Mating:  yellow  singed  X  short. 
4  cultures  (P  649,  674-5,  677). 

Non-cross-overs  (y  s  34 ;  si  40) 74 

Co.  region  1  (y  si  17;  s  24) 41 

Co.  region  2  (y  19;  si  s  21) 40 

Co.  region  1-2  (y  si  s  9 ;  4-  9) 18 

Total 173 

Per  cent  cross-overs,  y-si  34.1;  si— 3  33.5. 

Exp.  26. — Yellow  hairy  magenta. 

Mating:  yellow  hairy  X  magenta. 

1  culture  (V  866). 

Non-cross-overs  (y  ha  16;  m  19) 36 

Co.  region  1  (y  m  16;  ha  9) 26 

Co.  region  2  (y  ha  m  1 ;  -f  l) 2 

Co.  region  1-2  (y  0 ;  ha  m  1) 1 

Total 63 

Per  cent  cross-overs,  y-ha  41.3;  ha-m  4.8. 

Exp.  27. — Vermilion  magenta  forked. 

Mating:  vermilion  X  magenta  forked. 

2  cultures  (E  475-6). 

Non-cross-overs  (v  59;  m  f  48) 107 

Co.  region  1  (v  m  f  24;  -|-  28) 62 

Co.  region  2  (v  f  3;  m  3) 6 

Total 165 

Per  cent  cross-overe,  v-m  31.5;  m-f  3.6. 


Group  I. 


81 


Exp.  28. —  Vesiculated  hairy  niogenta. 

Mating:  vesiculated  maRcnta  X  hairy. 
4  cultures  (V  1054-55,  1061-62). 

Non-cross-overs  (vs  m  32;  ha  39) 71 

Co.  region  1  (vs  ha  22 ;  ni  24) 46 

Co.  region  2  (vs  0;  ha  m  2) 2 

Co.  region  1-2  (vs  ha  nil;-Hl) 2 

Total 121 

Per  cent  cross-overs,  vs-ha  39.6;  ha-m  3.3; 
counting  only  vs  flies,  vs-ha  41.8. 

Exp.  29. — Hairy  magenta  forked. 

Mating:  hairy  X  magenta  forked. 
4  cultures  (V  1114,  1116,  1119-20). 

Non-cross-overs  (ha  105;  m  f  53) 158 

Co.  region  1  (ha  m  f  1 ;  -|-  4) 5 

Co.  region  2  (ha  f  0;  m  2) 2 

Co.  region  1-2  (ha  ni  1 ;  f  0) 1 

Total 166 

Per  cent  cross-overs,  ha-m  3.6;  m-f  1.8. 

Exp.  30. — Magenta  forked  triangle. 

Mating:  magenta  forked  X  triangle. 
2  cultures  (P  911-12). 

Non-cross-overs  (m  f  109;  T  129) 238 

Co.  region  1  (m  T  1;  f  Ij 2 

Co.  region  2  (m  f  T  5;  +  24) 29 

Total 269 

Per    cent  cross-over.«,  m-f    0.7;    f-T    10.7; 
counting  only  T  flies,  f-T  3.7. 


Exp.  31. — Magenta  forked  droop. 

Muting:  magenta  forked  X  droop. 
4  cultures  (K  1270-1.  1310-11). 

Non-cross-overs  (m  f  50;  d  47) 97 

Co.  region  1  (ni  d  1 ;  f  1) 2 

Co.  region  2  (ni  f  d  15;  -1-  45)                    .  .  60 

Co.  region  1-2  (ni  1;  f  d  1).  .  .                   ..  2 

Total 161 

Per    cent   cross-overs   m-f   2.5;    f-d    38.6; 
counting  only  d  flies,  f-d  25.0. 

Exp.  32. — Triangle  short  droop. 

Mating:  Triangle  short  X  droop. 
4  cultures  (M  184,  205,  210,  225). 

Non-cro-ss-overs  (T  s  120;  d  117) 237 

Co.  region  1  (T  d  7;  s  6) 13 

Co.  region  2  (T  s  d  31 ;  -|-  32) 03 

Co.  region  1-2  (T  0;  a  d  2) 2 

Total 315 

Per  cent  cross-overs:  T-s  4.8,  s-d  20.6. 

Exp.  33. — Short  rugose  droop. 

Mating:  short  droop  X  rugose. 
6  cultures  (M  280,  283,  304-7). 

Non-cross-overs  (s  d  138;  r  149) 287 

Co.  region  1  (s  r  20;  d  15) 35 

Co.  region  2  (s  57;  r  d  11) 68 

Co.  region  1-2  (s  r  d  0:  -|-  19) 19 

Total 409 

Per    cent  cross-overs,  s-r    13.2;   r-d    21.3, 
coimting  all  flies;  counting  only  d  flies,  r-d,  6.7. 


Exp.  34. — Sepia  crossveinless  singed  short. 
Mating:  sepia  crossveinless  X  singed  short. 


Culture 

No. 

Non- 
cross- 
overs. 

Cross-overs  in  region. 

Total. 

1 

2 

3 

1-2              1-3 

1       2-3 

1-2-3 

se  c     si  s 

sesis 

c 

+ 

se  c  si  s 

!             ! 

se  c  8     si    '  se  c     si  s  ;  se  si     so 

1 

1 
1 

sec  si 

8 

se  s 

C  Bl 

M302 
M  308 

Total. . 

14       10 
12       15 

3 

7 

4 
4 

4 
5 

0        7       12        2         0 
4        6       14        1         1 

2         2 
1          3 

1 

1 

•> 

3 

1 

0 
0 

1 

0 

65 
76 

26       25 

10 

_'_ 

9 

4 

13       26 

3         1 

3         5 

1     3 

4 

0 

1  , 

141 

Per  cent  cross-overs:  se-c,  21.9;  c-si,  17.7;  si-e,  39.0. 


82 


Tabulation  of  Data. 

Exp.  35. — Sepia  crossveinless  short  rugose. 
Mating:  sepia  crossveinless  short  X  rugose. 


Cross-overs  in  region. 

Non- 
cross- 

Culture 

No. 

overs. 

1 

2 

3                  1-2 

1- 

-3 

2- 

-3 

1- 

2-3 

Total. 

r     sees 

se  r 

c  a 

seer 

s 

+ 

1 
1 

se  c  s  r  se  a      c  r 

se 

c  sr 

se  c 

a  r 

c 

sear 

M348 

18       12 

3 

4 

8 

13 

2 

1 

2         2 

1 

1 

5 

2 

0 

1 

75 

M  349 

14       15 

2 

9 

10 

12 

4 

0 

4         3 

1 

1 

5 

4 

3 

0 

87 

M  350 

18       12 

4 

6 

12 

14 

2 

0 

2         2 

0 

0 

2 

0 

0 

0 

74 

M351 

20       14 

7 

1 

8 

17 

4 

2 

0         5 

1 

0 

3 

0 

1 

1 

84 

M  352 
Total. . 

21       23 

2 

6 

9 

23 

2 

3 

5         0 

1 

0 

4 

2 

2 

2 

105 

91       76 

18 

26 

47 

79 

14 

6 

13       12 

4 

2 

19 

8 

6 

4 

425 

Per  cent  cross-overs:  se-c,  20.0;  c-s,  44.2;  s-r,  14.8. 

Exp.  36. — Yellow  crossveinless  vermilion  vesiculated. 
Mating:  yellow  crossveinless  X  vermilion  vesiculated. 


Culture 
No. 

Non- 
cross-overs. 

Cross-overs  in  region. 

Total. 

1 

2 

3 

1-2 

y  c            V  vs 

y  v  vs 

c 

y  c  V  vs          + 

y  c   vs 

V 

y 

c  V  vs 

P900 
P  901 ... . 
P902 
P903 
P904 

Total .  . 

22               28 
35               33 
24               16 
47               25 
39               39 

5 
5 
3 
6 
13 

4 

6 

16 

17 

6 

0                 0 
0                0 
0                0 
0                0 
0                1 

0 
1 
0 
0 
1 

0 
1 
0 
0 

1 

0 
0 
0 
0 
0 

1 

0 
0 
0 

0 

60 
81 
59 
95 
100 

167             141 

32 

49 

0                1 

2 

2 

0 

1 

395 

Per  cent  cross-overs:  y-c,  20.7;  e-v,  0.5;  v-vs  1.0;  counting  only  v-vs,  1.1. 

Exp.  37. — Yellow  hairy  magenta  forked. 
Mating:  yellow  hairy  X  magenta  forked. 


Culture 
No. 

Non- 
cross-overs. 

Cross-overa  in  region. 

Total. 

1 

2 

3 

1-2 

1- 

-3 

y  ha      m  f 

y  m  f 

ha 

y  hmf 

+ 

y  haf        m 

y       ha  m  f 

y  m 

haf 

V  1101 

V  nolo 

V  1102O 

V  1103 

Total 

14           7 
14           7 
19         20 
11         10 

6 

9 

11 

9 

11 
14 
21 
17 

0 
3 

1 
0 

2 
3 

0 

1 

0             0 

0  0 

1  0 
0             1 

0             1 
0             0 
0             1 

0              0 

2 
0 
2 

1 

0 

1 
2 

1 

43 
51 

78 
51 

58         44 

35 

63 

4 

6 

1             1 

0             2 

5 

4 

223 

Per  cent  cross-overs:  y-ha,  48.8;  ha-m,  5.4;  m— f,  4.9. 


Group  I. 


83 


Exp.  38. — Yellow  vesiculated  forked  rugose. 
Mating:  yellow  rugose  X  ve8iculat«d  forked. 


Culture 
No. 

Non- 
cross- 
overs. 

Cross-overs  in  region. 

ToUl. 

1 

2 

3 

1-2               1-3 

2-3 

1-2-3 

y  r      V8  f 

y  vsf     r 

yf 

vs  r 

y     vsf  r 

y  vsr      f 

-I-  yvafr 

v8     y  f  r 

y  vs     f  r 

V945 
V948 

Total. . 

15       13 
6        8 

1  9 

2  2 

10 
4 

13 
10 

7         8 
3         5 

0  5 

1  2 

4         0 
2         0 

5         2 
3         0 

1          1 
0         0 

94 

48 

21       21 

3       11 

14 

23 

10       13  I     1         7        6         0 

1 

8         2 

1          1 

142 

Per  cent  cross-overs:  y-vs,  21.1;  vs-f,  40.1;  f-r,  28.8;  counting  only  vs  flies,  y-vs,  7.1;  va-f.  47.1. 

Exp.  39. — Yellow  vesiculated  forked  glazed. 
Mating:  yellow  X  vesiculated  forked  glared. 


Non- 

Cross-overs 

in  region. 

Culture 
No. 

overs. 

Total. 

1 

2 

3         1       1- 

2 

1- 

3 

2 

-3 

1-2- 

-3 

y     V8fr« 

yvsfr« 

+ 

yfr« 

V8 

y  r«    VB  f 

y  V8 

lr« 

y  vsf 

r« 

yf 

V3r« 

yvsr* 

V947 

40       22 

1 

8 

8 

15 

10       11 

5 

0 

0 

3 

5 

6 

0 

1 

136 

V948 

3         6 

0 

2 

0 

3 

6        8 

0 

0 

2 

2 

4 

10 

1 

2 

48 

V950 

34       11 

10 

9 

12 

23 

20       16 

7 

1 

4 

4 

10 

4 

4 

2 

171 

V989 

6         1 

0 

2 

1 

4 

1         2 

0 

0 

1 

0 

0 

0 

0 

0 

18 

V996 

11         3 

0 

4 

1 

2 

3         2 

0 

0  1     0 

1 

0 

0 

0 

1 

28 

V996o 

16         2 

0 

2 

1 

6 

3         4 

0 

0        0 

1 

3 

2 

0 

1 

40 

V997 
Total. . 

16         3 

1 

0 

3 

2 

4         2 

1 

2        1 

0 

2 

1 

0 

0 

38 

126       47 

12 

27 

26 

54 

47       45      13 

3 

8 

11 

24 

23 

5 

7 

478 

Per  cent  crossovers:  y-vs,  17.9;  vs-f,  32.4;  f-r«,  35.5;  counting  only  vs  flies,  y-vs,  18.3;  vs-f,  45.9. 

Exp.  40. — Crossveinless  vermilion  mageiita  forked. 
Mating:  vermilion  X  crossveinless  magenta  forked. 


Non- 

Cross-overs 

in  region. 

Culture 
No. 

cross- 
overs. 

Total. 

1 

2                        3 

1-2 

2- 

-3 

v       c  m  f 

c  v 

mf 

c 

V  m  f 

cm 

vf 

cvm  f 

+ 

cf 

V  m 

E    986 

29         12 

0 

0 

18 

10 

0 

1 

0            0 

0 

0 

1 

70 

E    987 

36         28 

0 

0 

17 

15 

2 

0            0 

0 

2 

0 

100 

E    988 

69         21 

0 

0 

36 

20 

1 

1            0 

0 

0 

0 

138 

E    990 

17         17 

0 

0 

14 

2 

0 

1       1 

0 

0 

0 

52 

E    991 

56         29 

0 

0 

35 

23 

1 

0 

0 

0 

1 

0 

146 

E    992 

58         43 

1 

0 

28 

11 

1 

0 

0 

0 

1 

0 

143 

E    993 

46         29 

0 

0 

23 

23 

0 

0 

0 

0 

0 

1 

122 

E  1024 

32         14 

1 

0 

18 

13 

1 

0 

0 

0 

0 

0 

79 

E  1025 

33         18 

0 

0 

24 

16 

2 

0 

0 

0 

0 

0 

93 

E  1026 

33         14 

1 

0 

16 

17 

1 

2 

0 

0 

1 

0 

84 

E  1027 

44         16 

1 

0 

17 

8 

1 

1 

0 

0 

0 

0 

87 

E  1046 

53         22 

0 

0 

29 

14 

1 

1 

0 

0 

0 

0 

120 

E  1047 

26         19 

0 

1 

19 

15 

0 

2     ,       0 

0 

0 

0 

82 

E  1048 
Total.... 

32         28 

0 

0 

21 

13 

0 

2     ,       0 

0 

0 

0 

00 

554       309 

4 

1 

314 

200          11 

10 

1 

0 

5 

2 

1411 

Per  cent  cross-overs:  c-v,  0.4;  v-m,  36.9   m-f,  1.9. 


84 


Tabulation  of  Data. 


Exp.  41. — Vermilion  singed  magenta  forked. 
Mating:  vermilion  singed  X  magenta  forked. 


Culture 
No. 

Non- 
cross- 
overs. 

Cross-overs  in  region. 

Total. 

1 

2 

3 

1-2 

1-3 

2 

-3 

V  si       m  f 

si 

V  m  f 

V  si  m  f 

+ 

v  si  f       m 

v     m  si  f 

vm 

sif 

f 

V  m  si 

P  645 
P646 
P648 
P678 
P679 

Total .  . 

28         28 
27         20 
26         22 
9           5 
25         10 

3 
9 
6 
3 
3 

5 
7 
2 
0 
5 

to  o  to  to  to 

11 

11 

10 

3 

5 

0           2 
0           0 
0           1 

0  1 

1  1 

0          0 
0           1 
3           0 
0           0 
0           1 

0 
1 
0 
1 
0 

1 
0 
0 
0 
0 

0 
0 
0 
0 
0 

2 
2 
3 
0 
0 

82 
80 
75 
22 
53 

115         85 

24 

19 

8 

40 

1           5 

3           2 

2 

1 

0 

7 

312 

Per  cent  cross-overs:  v-si,  16.3;  si-m,  19.2;  m-f,  5.1. 


Exp.  42. — Vesiculated  hairy  magenta  forked. 
Mating:  vesiculated  hairy  X  magenta  forked. 


Culture 
No. 

Non- 
cross- 
overs. 

Cross-overs  in  region. 

Total. 

1 

2 

3 

1-2 

vs  ha         m  f 

vsmf 

ha 

vsha  mf      + 

vshaf 

m 

vs 

ham  f 

V  1143 

V  1143a 

V  1144 

V  1147 

Total .... 

35             30 

19               9 

10             11 

9             10 

5 
5 

4 

4 

14 
15 

8 
9 

1              5 
0               1 
0               3 
0               2 

0 
0 
0 
3 

1 
0 
0 

1 

1 
0 
0 
0 

0 
0 

2 
0 

92 
49 
38 
38 

73             60 

18 

46 

1             11            3 

2 

1 

2 

217 

Per  cent  cross-overs:  vs-ha,  30.9;  ha-m,  6.9;  m-t,  2.3;  counting  only  vs  flies,  vs-ha,  19.8. 

Exps.  43  AND  44. — Vesiculated  magenta  forked  rugose. 
Mating:  vesiculated  forked  X  magenta  rugose. 


Cross-overs  in  region. 

Culture 

Non- 
cross- 

No. 

overs. 

1 

2 

3 

1-2 

1- 

3 

2- 

-3 

1-2- 

3 

Total. 

vs  f    m  r 

vsmr 

f 

vs  r 

mf 

vsf  r    m 

vem  f     r 

vs  m 

f  r 

vs 

mf  r 

vs  m  f  r 

+ 

V  923 

20       29 

14 

14 

2 

0 

13 

7 

1         1 

5 

3 

0 

0 

0 

0 

109 

V  924 

39       40 

6 

15 

0 

1 

11 

8 

1         0 

3 

6 

0 

1 

1 

0 

132 

V  926 

15       17 

5 

3 

0 

0 

3 

4 

0         0 

1 

2 

1 

0 

1 

0 

52 

V  927 

44       36 

11 

7 

1 

0 

12 

14 

0         0 

6 

1 

0 

0 

2 

0 

134 

V  928 

3         5 

0 

1 

1 

0 

1 

1 

0         0 

1 

0 

0 

0 

0 

1 

14 

V  929 

21       31 

7 

4 

0 

2 

5 

10 

1         1 

4 

2 

1 

0 

0 

0 

89 

V930 

20       15 

1 

5 

0 

0 

1 

8 

0         1 

3 

0 

0 

1 

0 

0 

65 

V931 

12         4 

1 

3 

0 

1 

0 

3 

0         1 

2 

0 

0 

0 

0 

0 

27 

V933 

17       19 

2 

4 

0 

2 

1 

7 

0         0 

3 

0 

0 

0 

1 

0 

56 

V934 
Total. . 

9       22 

4 

3 

0 

0 

3 

7 

0         0 

1 

2 

0 

0 

1 

0 

52 

200     218 

51 

69 

4 

6 

50 

69 

3         4 

29 

16 

2 

2 

6 

1 

720 

Group  I. 

Exps.  43  .\ND  44. — Vesiculated  magenla  forked  rugose — Continued. 
Mating:  vesiculated  magenta  X  forked   rugose. 


85 


Non- 

Cross- 

overs 

in  region. 

Culture 
No. 

cross- 
overs. 

Total. 

1 

2 

3 

1- 

-2 

1- 

-3 

2-3 

1-2 

-3 

vem    f  r 

vsf  r    m 

vsmfr 

+ 

vsm  r    f 

V8 

mf  r 

vaf 

m  r 

vamf 

r 

vsr 

mf 

V917 

8         3 

3 

6 

0 

1 

1         2 

1 

0 

0 

0 

0 

1 

0 

0 

26 

V918 

7         3 

1 

4 

0 

1 

4         3 

0 

0 

0 

3 

0 

0 

1 

0 

27 

V921 

38       29 

11 

27 

2 

0 

7        10 

1 

1 

6 

5 

0 

0 

3 

0 

140 

V935 

5         5 

7 

5 

1 

1 

1          5 

0 

2 

1 

1 

0 

0 

0 

0 

34 

V936 

17       12 

14 

19 

0 

0 

6        11 

0 

0 

6 

4 

0 

0 

0 

0 

89 

V937 

24       16 

17 

21 

1 

3 

5        11 

1 

0 

5 

6 

0 

0 

1 

1 

112 

V938 

10       12 

8 

8 

0 

0 

6         3 

0 

1 

'> 

1 

0 

0 

0 

3 

54 

V  939 

11         9 

6 

3 

1 

2 

3          5 

1 

0 

3 

3 

0 

0 

0 

0  1 

47 

V940 

17       12 

4 

7 

1 

2 

9         6 

1 

0 

3 

4 

0 

0 

0 

0 

65 

V941 

11         6 

5 

3 

0 

2 

2         6 

0 

0 

2 

1 

0 

0 

0 

0 

38 

V942 

12       10 

8 

12 

0 

1 

2         8 

2 

0 

6 

6 

0 

0 

0 

0 

67 

V943 

29       12 

14 

15 

0 

0 

6         8 

1 

1 

3 

7 

0 

1 

0 

0 

97 

V  944 

20        15 

13 

14 

0 

4 

6       10 

0 

1 

4 

4 

0 

0 

1 

0 

92 

V  949 
Total. . 

Grand 

23        11 

13 

18 

1 

3 

4       13 

2 

2 

3 

3 

0 

3 

0 

1 

100     ; 

232     155 

124 

162 

7 

20 

62     100 

10 

8 

44 

48 

0 

5 

6 

5 

988 

Total. . 

432     373 

175 

221 

11 

26 

112     169 

13 

12 

73 

64 

2 

7 

12 

6 

1708 

Per  cent  cross-overs:  vs-m,  33.7;  m-f,  5.2;  f-r,  26.0;  counting  all  flies;  va-m,  32.8,  counting  only  v3  flies. 

Exp.  45. — Singed  magenta  forked  short. 
Mating:  singed  short  X  magenta  forked. 


Culture 
No. 

Non- 
cross- 
overs. 

Cross-overs  in  region. 

Total. 

1 

2 

3 

1-2 

1-3 

■» 

-3 

si  8       m  f  si  m  f 

s 

sif 

m  s 

si        m  f  s 

sims        f 

si  m  f  3 

+ 

si  f  8 

m 

M  385 
P    916a 

Total .... 

29         19        5 
20         28        3 

18 
11 

1 
0 

1 

0 

9            1 
9            2 

1           0 
0           1 

0 
0 

5 
5 

0 
0 

0 

3 

89 

82 

49          47        8 

1 

1 

29 

1 

1 

18           3 

1           1 

0 

10 

0 

3 

171 

Per  cent  cross-overs:  si-m,  28.6;  m-f,  4.1;  f-s,  19.8. 

Exp.  46. — Yellow  crossveinless  vermilion  magenla  forked. 
Mating:  yellow  crossveinless  X  vermilion  magenta  forked. 


Non- 

Cross-overs  in  region. 

1 

Culture 
No. 

cross- 
overs. 

1 

2 

3             1             4 

1- 

-3          1 

y  c      V  m  f 

y  vm  f 

c 

J'  c  v  m  f 

+ 

ycmf      v    1     ycf 

v  m 

y  V 

mcf 

L721 

17          15 

7 

8 

0 

0 

5         15 

1 

1 

2 

0 

L  722 

32          13 

•> 

10 

0 

0 

15          17 

1 

0 

4 

1 

L724 

58         58 

13 

15 

0 

1 

28         42 

o 

6 

<» 

a 

L725 

29          17 

6 

11 

0 

0 

8         20 

f) 

0 

2 

3 

L726 

27          15 

4 

3 

0 

0 

15           9 

0 

0 

.1 

•y 

E916 

17          12 

0 

4 

1 

0 

2          12 

0 

0 

1 

0 

E  918 
Total. 

3            4 

1 

1 

0 

0 

0           2 

0 

0 

0 

0 

183        134 

33 

52 

1 

1           73        117             4 

7 

21 

9 

86 


Tabulation  of  Data. 


Exp.  46. — Yellow  crossveinless  vermilion  magenta  forked. — Continued. 
Mating:  yellow  crossveinless  X   vermilion  magenta  forked. 


Culture 
No. 

Cross-overs  in  region. 

Total. 

2-3 

3-4 

1-2-3 

1- 

-3-4 

y  c  v 

mf 

ycm            vf      jymf            cv 

y  v  f 

c  m 

L721 

L722 
L724 
L725 
L726 
E916 
E918 

Total. 

0 
0 
0 
0 
0 
0 
0 

0 
0 
0 
0 
0 

1 

0 

0                 0 
0                 1 
0                 0 
0                 0 
0                 0 
0                 0 
0                 0 

0                 0 
0                0 
0                1 
0                0 
0                0 
0                0 
0                0 

0 
0 

1 

0 
0 
0 
0 

0 
0 
0 
0 
0 
0 
0 

71 
96 
237 
96 
78 
50 
11 

0 

1 

0                 1 

0                1 

1 

0 

639 

Per  cent  cross-overs:  y-c,  18.3;  c-v,  0.6;  v-m,  35.0,  m-f,  2.0. 

Exp.  47. — Yellow  vesiculated  magenta  forked  ritgose. 
Mating:  yellow  magenta  X  vesiculated  forked  rugose. 


Culture 

No. 

Non- 
cross- 
overs. 

Cross-overs  in  region. 

1 

2 

3                    4 

1-2 

1-3 

y  m     ve  f  r 

y  vs  f  r  m 

y  f  r     vs  m 

ymfr     vsymr     vsf 

y  vsm 

fr 

y  vs  m  f  r 

V958 
V959 
V960 
V  962 

Total. . 

29  5 

30  7 
14           7 
25         12 

3           4 
3           8 
5         11 
2           5 

3         10 

6         15 

5         10 

11           7 

0           2 
0           1 
0           0 
0           4 

12           0 
7           3 
6           5 

9         12 

4 
0 
3 
1 

0 
0 
0 
2 

1           0 
0          0 

0  0 

1  0 

98         31 

13         28 

25         42        0           7      34         20 

8 

2 

2           0 

Culture 

No. 

Cross-overs  in  region. 

Total. 

1-4 

2-3 

2-4 

1-2-4 

3-4 

1-3- 

-4 

y  vs  f    m  r 

vemfr  y 

vs  m  r    y  f 

yvsmr    f 

y  m  f   vs  r 

y  vsr 

mf 

V958 
V959 
V960 
V962 

Total. . 

0  2 

1  1 
1         2 
3         1 

0         2 
0         1 
0         0 
0         3 

2         1 

1  2 

2  3 
5         5 

1         2 
0         1 
0         5 
0         1 

0        0 
0         1 
0         0 
0         0 

0 
1 
0 
0 

0 
0 
0 
0 

83 

89 

79 

109 

5         6 

0         6 

10       11 

1         9 

0         1 

1 

0 

360 

Per  cent  cross-overs:  y-vs,  20.8;  vs-m,  31.6;  m-f,  4.7;  f-r,  27.2;  counting  only  vs  flies,  y-vs, 
21.2;  vB-m,  43.2. 


Group  I. 


87 


Exp.  48. — Sepia  erossveinless  singed  magenta  forked  short. 
Mating:  eepia  crossveinless  singed  ehort  X  magenta  forked. 


Culture 
No. 

Non- 
cross-overs. 

Crosa-overs  in  region. 

1 

2                        3 

4 

6 

se  c  si  s 

mf 

se  m  f 

c  si  s 

se  c  m  f 

si  s 

se  c  si  m  f 

B 

se  c  Bi  f 

m  B 

Be  c  si 

m  f  a 

P908 
P909 
P910 
P917 
P918 

Total 

12         15 
9         14 

25         36 
1         25 

10         22 

6           4 

3  1 

4  4 
6           0 
3           3 

2         3 

2  2 

3  4 

4  0 

7         2 

3           9 

5           7 
5         11 
1           7 
1         11 

2           0 
0           1 
0           0 
0           0 
0           0 

3 
6 
6 
2 
11 

1 
0 
0 
0 

1 

57       112 

22          12 

18       11 

15         45 

2           1 

27 

2 

Culture 
No. 

Cross-overs  in  region. 

1-2 

1-3 

1-4 

1-5 

2-3 

2- 

4 

se  si  s 

cm  f 

se  s 

c  si  m  f 

se  m  s 

c  si  f 

se  m  f  s 

c  si 

se  c  9 

si  m  f 

se  c  m  6 

Bif 

P908 
P909 
P910 
P917 
P918 

Total 

0        0 
0         1 
0        3 
0        0 
0         2 

2  2 
1           0 

3  4 
1           1 
0           3 

0  0 

1  0 
0           0 
0           0 
0           0 

0           1 
0           4 
0           2 

0  0 

1  0 

0         0 

0  0 
3         0 

1  1 
1         2 

0 
0 
0 

0 

1 

0 
0 
0 
0 
0 

0        6 

7       10 

1         0 

1           7 

5         3 

1 

0 

Culture 
No. 

Cross-overs  in  region. 

2-5 

3-4 

3-5 

4-5 

1-2-3 

1-2 

-5 

se  c  m  f  s 

si 

se  c  si  m  s 

f 

se  c  si  m  f  8 

+ 

se  c  si  f  B 

m 

se  si  m  f 

C  B 

aesi 

c  m  8  f 

P908 
P909 
P  910 
P917 
P918 

Total 

0           3 
0           2 
0           0 
0           2 
0           1 

0           0 
0           0 
0           0 

0  0 

1  0 

1          3 

0  3 

1  1 
0         5 
0         3 

0          0 
0          1 
0           2 
0          0 
0          0 

0          0 

0  1 

1  0 
0          0 

0            1 

0 
0 
0 
0 
0 

0 
1 
0 
0 
0 

0           8 

1           0 

2        15 

0          3 

1           2 

0 

1 

88 


Tabulation  of  Data. 


Exp.  48 — Sepia  crossveinless  singed  magenta  forked  short — Continued. 
Mating:  sepia  crossveinless  singed  short  X   magenta  forked. 


Culture 
No. 

Cross-overs  in  region. 

1-3-5 

3-4-5 

1-2-3-4 

1-3 

-4-5 

Total. 

se 

0  si  m  f  s 

se  c  si  m 

f  8 

se  si  m  8 

of 

se  f  3 

0  m  si 

P908 
P909 
P910 
P917 
P918 

Total 

0             0 
2             1 

0  0 

1  0 
0             0 

0             0 

0  0 

1  0 

0  0 

1  0 

0  0 

1  0 
0             0 
0             0 
0             0 

0 
0 
0 
0 
0 

0 
0 
0 
0 

1 

72 
69 
118 
58 
89 

3             1 

2              0 

1             0 

0 

1 

406 

Percent  cross-overs:   se-c,  18.7;     c-si,  14.0;  si-m,  28.0;  m-f,  3.2;  f-s,  17.9. 

Exp.  49. — Oblique  magenta  forked  short. 
Mating:  oblique  short  X  magenta  forked. 


Culture 
No. 

Non- 
cross- 
overs. 

Cross-overs  in  region. 

Total. 

1 

2                  3 

1-2 

1-3 

2-3 

OS      mfomf      8 

of       ms     o      mfs 

om  8       f 

0  m  f  3      -|- 

o  f  8      m 

M  344         19       23        0       12 

'                    1 

0         2        3         2        0         1 

0         2        0          1 

65 

Per  cent  cross-overs:  o-m,  35;  m-f,  9;  f-s,  12;  counting  only  not-o  flies. 


Exp.  50. — Sepia  crossveinless  oblique  short. 
Mating:  sepia  crossveinless  X  oblique  short. 


Culture 
No. 

Non-oblique  flies. 

Total. 

Non- 
cross- 
overs. 

Cros.s-overs  in  region. 

Oblique 
flies. 

1 

2 

3          1-2 

1-3 

2-3 

1-2-3 

se  c 

c 

+      se  c  s      se 

c  s 

s 

se  8 

O  8 

not-s 

M244 
M246 

Total... 

10 

7 

3 

2 

1 
2 

3          0 

7          0 

3 
3 

1 
1 

0 

1 

21 
23 

9              5 
0              0 

17 

5 

3           10          0 

6 

2 

1 

44 

9              5 

Per  cent  cross-overs:  se-c,  27;  c-o,  14;  o-a,  43.2;  counting  only  not-o  flies. 


Group  I. 


89 


Exp.  51. — Oblique  singed. 
Mating:  oblique  X  singed. 


Culture 
No. 

Non- 
cross-overa. 

Cross-overs. 

Total. 

o               si 

o  si            + 

M394 

23             23 

0                 2                      48 

Per  cent  cross-overs:  o-si,  4.2. 


Exp.  52. — Sepia  oblique  singed  short. 
Mating:  sepia  oblique  short  X  singed. 


Culture 
No. 

Non- 
cross- 
overs 

Cross-overs 

m  region. 

Total 

1 

2 

3 

1-3 

2-3 

se?  OB     si 

se  si 

O  8 

se?  o  si 

s 

se?  o    si  8 

se  si  8    o 

se?  o  si  B 

+ 

M  392 
M  399 
M  400 

12       19 
7       14 
3         5 

5 
6 
1 

1 
1 
0 

1 
0 
0 

7         11 
7          4 
1           0 

1 
1 
0 

coo 

0 
2 
1 

57 
42 
11 

Total .  .  . 
Correction" 

22       38 
15       .. 

12 

(?) 

7 

2 

1 

15         15 

2      (?) 

0 

3 

110 

Corrected 
total .... 

15       38 

12 

7 

2 

1 

15         15 

2         0 

0 

3 

110 

Per  cent  cross-overs:  se-o,  19.1;  o-si,  5.4;  si-s,  31.8;  counting  all  flies,  se-o.  19.7;  o-si.  5.6; 
si-s,  28.1,  counting  only  not-o  flies. 
"After  apportioning  se,  o,  and  o. 

Exp.  53. — Sepia  oblique  singed. 
Mating:  sepia  oblique  X  singed. 


Culture 
No. 

Non- 
cross-overs 

Cross-overs  in  region. 

Total 

1 

2 

1 

-2 

se?  o       si 

Be  si 

o 

se?  o  si     + 

se 

o  si 

M  393 
M  395 

14         22 
21         28 

3 
9 

1             2 
1             2 

0 

1 

42 
62 

Total 

Correction" 

35         50 
30 

12 

(?) 
5 

2              4 

1 

(?) 

104 

Corrected 
total .... 

30         50 

12 

5 

2              4 

1 

0 

104 

1 

Per  cent  cross-overs:  ae-o,  17.3;  o-si,  6.7;  counting  all  flies,  se-o,  19.4;  o-si,  7.4.  counting  only 
not-o  flies. 

o  After  apportioning  ae  o,  and  o. 


90 


Tabulation  of  Data. 


Linkage  Experiments  on  Genes  Group  II. 
(Experiments  54  and  55.) 


Exp.  54. — Confluent  concave. 

Mating:  confluent  X  concave. 
2  cultures  (V  674,  729). 

Non-cross-overs  (C  59;  cc  64) 123 

Cross-overs  (C  cc  36;  +  54) 90 

Total 213 

Per  cent  cross-overs,  C— cc  42.2. 


Exp.  55. — Confluent  broken. 

Mating:  confluent  X  broken. 
2  cultures  (M  299,  318). 

Non-cross-overs  (C  74 ;  b  65) 139 

Cross-overs  (C  b  38;  +  55) 93 

Total 232 

Per  cent  cross-overs,  C— b  40.0. 


Linkage  Experiments  on  Genes  in  Group  III. 
(Experiments  56  to  61.) 


Exp.  56. — Scaly  spread. 

Mating:  scaly  X  spread. 

5  cultures  (M  363-5.  368-9). 

Non-cross-overs  (S  86;  sp  87) 173 

Cross-overs  (S  sp  23;  -1-  31) 54 

Total 227 

Per   cent   cross-overs,  S-sp   23.8;   counting 
only  S  flies,  S-sp  21.1. 

Exp.  57. — Scaly  hunch. 

Mating:  scaly  X  hunch. 
2  cultures  (L  421,  426). 

Non-cross-overs  (S  55 ;  h  44) 99 

Cross-overs  (S  h  9 ;  +  26) 35 

Total 134 

Per    cent    cross-overs,  S— h    26.1;    counting 
only  S  flies,  S-h  14.0. 

Exp.  58. — Scaly  telescoped. 

Mating:  scaly  X  telescoped. 
2  cultures  (V  1256,  1258). 

Non-cross-overs  (S  145;  t  168) 313 

Cross-overs  (S  t  95;  -I-  142) 237 

Total 650 

Per    cent    cross-overs,  S— t    43.0;    counting 
only  S  flies,  S-t  39.6. 

Exp.  59. — Spread  garnet. 

Mating:  spread  X  garnet. 
2  cultures  (M  379,  386). 

Non-cross-overs  (sp  39 ;  G  43) 82 

Cross-overs  (sp  G  24;  -|-  35) 59 

Total l41 

Per  cent  cross-overs,  sp-G  41.8. 


Exp.  60. — Scaly  hunch  telescoped. 

Mating:  scaly  X  hunch  telescoped. 

8  cultures  (E  519-20,  522-24,  530,  M  252, 295). 

Non-cross-overs  (S  261 ;  h  t  279) 540 

Co.  region  1  (S  h  t  123 ;  -|-  260) 383 

Co.  region  2  (S  t  68;  h  64) 132 

Co.  region  1-2  (S  h  27;  t  55) 82 

Total 1,137 

Per    cent    cross-overs,  S-h   40.8,    h-t    18.8; 
counting  only  S  flies,  S— h  31.3. 

Exp.  61. — Scaly  hunch  telescoped  garnet. 

Mating:  scaly  hunch  telescoped  X  garnet. 
2  cultures  (M  375-6). 

Non-cross-overs  (S  h  t  32;  G  60) 82 

Co.  region  1  (S  G  19;  h  t  15) 34 

Co.  region  2  (S  h  G  1 ;  t  2) 3 

Co.  region  3  (  S  h  t  G  23;  -f-  33) 66 

Co.  region  1-2  (S  t  2 ;  h  G  4) 6 

Co.  region  1-3  (S  5 ;  h  t  G  22) 27 

Co.  region  2-3  (S  h  2;  t  G  4) 6 

Co.  region  1-2-3  (S  t  G  0;  h  5) 6 

Total 219 

Per    cent    cross-overs,  S-h    32.8,    h-t    9.1, 
t-G  42.9;  counting  only  S  flies,  S-h  30.9. 


Linkage  Experiments  on  Genes  in  Group  IV. 
(Experiments  62  and  63.) 


Exp.  62. — Pinched  hump. 

Mating:  pinched  hump  X  wild-type. 

(a)  (P  hp  -  +)  9  X  P  hp  cj^  ,  1  culture  (L  339) 

Non-cross-overs  P  hp  25;  (P)  32    57 

Cross-overs  P  0;  (P)  hp  0    0 

Total 57 

(6)  (P  hp  -  +)  9  X  hp  cf,  2  cultures  (L  350, 
(393). 

Non-cross-overs   (P)   hp  38;  -)-  56 94 

Cross-overs  (P)  1?;  hp  0 21 

Total 95 

Per  cent  cross-overs,  P-hp  0.0. 


Exp.  63. — Pinched  acute. 

Mating:  pinched  X  acute. 

9  cultures  (L  565,  579; E  971-2, 1089,  1096-99). 

Non-cross-overs  (P)  515;  ac  463 978 

Cross-overs  (P)  ac  0;  -|-  0 0 

Total 978 

Per  cent  cross-overs,  P— ac  0.0. 


Group  V. 


91 


Linkage  Experiments  on  Genes  in  Group  V. 
(Experiments  64  to  70.) 


Exp.  64. — Fused  interrupted. 

Mating:  fused  X  interrupted. 

6  cultures  (E  788,  826,  953,  974,  1116-7). 

Non-cross-overs  (fu  343 ;  i  279) 622 

Cross-overs  (fu  i  64;  +  233) 297 

Total 919 

Per  cent  cross-overs,  fu-i,  counting  only  i, 
18.6. 

Exp.  65. — Fused  branched. 

Mating:  fused  X  branched. 
2  cultures  (E  606,  614). 

Non-cross-overs  (fu  111;  B  111) 222 

Cross-overs  (fu  B  28 :  +  21) 49 

Total 271 

Per  cent  cross-overs,  fu-B  18.0. 


Exp.  66. — Fused  approximated. 

Mating:  fused  approximated  X  wild-type. 
4  cultures  (M  8-11). 

Non-cross-overs  (fu  and  fu  a  225;  +  183)    408 
Cross-overs  (fu  not  a  13;  a  97) 110 

Total 518 

Per    cent    cross-overs,    fu-a    counting    only 
not  fu  flies,  35.0. 

Exp.  67. — Interrupted  branched. 

Mating:  interrupted  X  branched. 

6  cultures  (E  902,  924,  953,  974,  1116-7). 

Non-cross-overs  (i  163;  B  149) 312 

Cross-overs  (i  B  4 ;  +  199) 203 


Total 515 

Per  cent  cross-overs,  i-B,  counting  only  i. 


2.4. 


Exp.  68. — Interrupted  approximated. 
Mating:  interrupted  approximated  X  wild-type. 


Culture 

Non- 
cross-overs. 

Cross-overs. 

Doubtful 
class. 

Total. 

J\o. 

ia          -1- 

i           a 

i.  a? 

A. 

'E  915 
E  974 

Tntal 

80         106 
36           16 

16           9 
2         23 

211 
77 

116         122 

18         32 

288 

B 

M     5 
M     6 
M     7 
M  12 

Total 

42           80 
31         107 
22         100 
37         106 

4  13 

5  19 

10  22 

11  23 

40 
56 
64 
50 

179 
218 
218 

227 

132         393 

30         77 

210 

842 

Grand  total 

248         515 

48       109 

210 

1 ,  130 

r 

Fotal 

175? 

423         515 

35?      ... 
83       109 

1,130 

Per  cent  cross-overs,  after  apportioning  doubtful  flies,  i-a  17. 


Exp.  69. — Branched  ruffled. 

Mating:  branched  X  ruffled. 

4  cultures  (M  314,  353-4,  367). 

Non-cross-overs  (B  97 ;  ru  103) 200 

Cross-overs  (  B  ru  88;  -fllO) 198 

Total 308 

Per  cent  cross-overs,  B-ru  49.7. 


92 


Tabulation  of  Data. 


Exp.  70. — Fused  branched  approximated. 
Mating:  branched  X  fused  approximated. 


Culture 
No. 

Non- 
cross-overs. 

Cross-overs  in  region. 

Doubtful 
classes. 

Total. 

1 

2 

1-2 

B     fu  a 

Bfu 

a 

Ba        fu 

+ 

B  fu  a 

fu  a?     B  fu  a? 

M  118 
M  135 
M  141 
M  160 

Total. 

Total. 

21         8 
45       36 
37       33 
33       35 

3 
5 
4 

g 

1 

9 

10 

3 

5           8 

21  21 

24         19 

22  18 

2 
12 
11 

7 

0 
4 

4 
6 

0             0 

7             0 

2             5 

11             0 

48 
160 
149 
144 

136     112 

21 

23 

72         66 

32 

14 

20             6 

501 

13? 
136     125 

3? 
24 

23 

7? 
72         73 

32 

2? 
16 

•  • 

501 

Per  cent  cross-overs,  after  apportioning  doubtful  classes,  fu-B  19.0;  B-a,  38.5;  or  B-fu,  19.0; 
fu-a,  38.5. 


LITERATURE  CITED. 
Bridges,  C.  B.,  and  T.  H.  Morgan. 

1919.  The  second  chromosome  group  of  mutant  characters.    Cameme  Inst    Wash 

Pub.  278:  123-304. 
Bridges,  C.  B. 

1921.  Genetical  and  cytological  proof  of  non-di.sjunction  of  fho  fourth  chromosome 

of  D.  melanogaster.     Proc.  Nat.  .\ca<l.  Science,  vol.  7,  p.  180. 
Detlefsen,  J.  a. 

1920.  Is  crcssing  over  a  function  of  distance?     Proc.  Nat.  Acad    Sciences    vol    6- 

663-673. 
Dexter,  J.  S. 

1919.     The  analysis  of  a  case  of  continuous  variation  in  Drosophiln  by  a  study  of  its 
linkage  relations.    Araer.  Nat.,  vol.  XLMIl,  pp.  712-758. 
Federley,  Harry. 

1914.  Ein    Beitrag   zur    Kenntnis    der   Spennatogone.se    hei    Mischlingm    rwinchen 

Elten  verschiedener  systematischer  \'er\vandt.schaft.     (Xwer-iigt  uf  I'in.Hka 
Vetenkaps — Societetens  Forliandlingar  56:  .Afd.  \.  N.:  0  13. 

1915.  Chromosomenstudien    an    Mischlingen.      Ofver.sigt    af    Kin.«ka    Votonkaps — 

Societetens  Forhandhngar  57:  Afd.  A.  N.:  0  26. 
Fisher,  R.  A. 

1922.  The  systematic  location  of  genes  by  means  of  crossover  ob.servations.     \n\vT. 

Nat.,  LVI:  406-411. 
Gowen,  Marie  S.,  and  John  W.  Gowen. 

1922.     Complete  linkage  in  Drosophila  melanogaster.    Amer.  Nat.,  56:  286-288. 
Harrison,  J.  W.  H.,  and  L.  Doncaster. 

1914.     On  hybrids  between  moths  of  the  Geometrid  sul)familv  Bistoninap,  etc.    Jour. 
Genet.,  3:  234. 
Harvey,  Ethel  Browne. 

1916.  A  review  of  the  chromosome  numbers  in  the  Metazoa.    Jour.  Mori>h.,  28:  l-<>3. 
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